’62 BRIT-PLEX 45W

A S S E M B LY I N S T R U C T I O N SWith loads of helpful tips!

’62 BRIT-PLEX 45W A M P L I F I E R K I T

ORIGINAL BRITISH CIRCUIT

The amp thatstarted a revolution

stewmac.com 2 © 2019 StewMac

Contents

About this iconic amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Parts list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Tools and supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Amp voltages are seriously dangerous! . . . . . . . . . . . . . . . . . . . . . . . . . . 6

How to use a snuffer stick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

How to read resistor values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Capacitor values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Complete wiring diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Prepping the turret board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Tips for great soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Installing the chassis-mounted components . . . . . . . . . . . . . . . . . . . 11

Wrapping parts onto the turret board . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Installing the turret board in the chassis . . . . . . . . . . . . . . . . . . . . . . . 37

Installing parts and preparing for testing . . . . . . . . . . . . . . . . . . . . . . 42

Testing and troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Final assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Tips for using this amp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Photograph of completely wired chassis . . . . . . . . . . . . . . . . . . . . . . . 47

Learning more: secrets revealed in the schematic . . . . . . . . . . . . . . 48

Circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

More iconic amp kits from StewMac . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Full page wiring diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Tube replacement chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

COPYRIGHT WARNINGThis material is protected by copyright and has been created by and solely for the purposes of StewMac . You may not sell, alter or further reproduce any part of this material, or distribute it to any other per-son . Where provided to you in electronic format, you may only print from it for your own private use . Failure to comply with the terms of this warning exposes you to legal action for copyright infringement .

How to build this kit!


’62 BRIT-PLEX 45W AMPLIFIER KIT ORIGINAL BRITISH CIRCUIT

This amp is an ICONThis is the JTM45 circuit, the very first circuit produced by Marshall and modeled after a 5F6A Fender Bassman . To keep the weight manageable, this amp was designed as a head to pair with a separate 4x12 speaker cabinet .

By the mid-60s the JTM45 had taken the crown from the AC30 as the must-have British amp . While it might not have as much grit and guts as the subsequent Marshall amps, this is the seminal circuit of a musical empire .

StewMac ICON KITS bring classics that are no longer made, or are simply unaffordable, within reach . And the best part is you get to build them with your own hands .

We give painstaking attention to parts selection, authentic materials, and instantly recognizable details—everything that makes the originals so sought after .

Build it with StewMacThese immersive instructions walk you through every step of creating your ’62 Brit-Plex . And you’ll learn a lot, gaining a deep knowledge of your amp’s inner workings .

Follow our steps closely for safety, too: we’ve carefully laid out a path that even newcomers can follow in handling electrical components .

Building an amp can seem daunting, but nobody makes it easier than StewMac . Watch for helpful tips along the way, too—we’re here to help!

Let’s get building!

Iconic British tone is now in your hands

Be excited!Your new StewMac ’62 Brit-Plex will be a blast to play through and even more fun to build .

This amp is favored by blues and rock guitarists for its rich, articulate clean tones and exceptional sustain: creamy, warm and a little crispy . Rich in harmonic feedback, this was the amp that started a rock and roll revolution .


Here’s how to build this amp!

Wiring goes like this:1. First, you’ll wrap the leads, connecting them without solder. 2. Then double-check all the connections. Don’t rush!3. When everything checks out, it's time to solder. The numbered steps tell you when.

Get the turret board ready, starting at Step 1 on page 9.You’ll prep the metal chassis too.

Learn more:You don’t need to read the schematic, but it’s fun! See how your guitar’s signal gets processed into sound on page 49.

Sort your components by type, using the parts list.Quick look:

OutputGain Processing Gain GainProcessing Negative feedback

See page 9

#00000 © 2019 StewMac

GroundJackTransformer Preamp tube

plategrid

cathode

Power tube

grid

plate

cathode

screen

Capacitor Electrolytic Cap. DiodeResistor Potentiometers Rectifier tube

plate cathode

filamentplate

Shieldedcable

’62 BRIT-PLEX45WO R I G I N A L B R I T I S H C I R C U I T

Output

Gain

Gain Gain

Power

Processing Processing

Pow

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Negative Feedback

BASS

TREBLE

PRESENCE

VOLNORM VOL

BRIGHT

MID

6V5V

MainsSTANDBY

FUSESlow-blow1 Amp

FUSESlow-blow500 mA

LIGHT120V

TRANSFORMERMojo 18W power

V65AR4

32μF

.022μF

.1μF

.1μF

250μ

F

.022

μF

.022

μF

.022μF

.022μF68K

68K

68K

68K

250pf

10K 2W 10K 2W

1K 5

W

470Ω

2W

470Ω

2W

500p

f

32μF

32μF

32μF

8μF

8μF

220K

15K1N4007 10KL

68K

.1μF

.1μF

1M

1MA

1M

220K

220K

25KL

5KL

10K

5.1K

5.1K

100K

100K

56K

100K

820Ω

820Ω

100K

250K

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Hardware

r (4) 10-32 machine screw, 1-1/2"r (4) 10-32 locknut

r (6) 8-32 machine screw, 1/4"r (10) 8-32 locknut


r (4) 4-40 threaded standoff, 1/2"


r (2) Switch mounting nut

r (2) Filter cap mounting clamp

r (3) Rubber grommet

Capacitors & diode

r (1) 47pF 500V silver mica



r (4) .1μF 600V Mojo Dijon



r (2) 8μF 150V Sprague Atom

r (1) 250μF 25V aluminum electrolytic

r (2) 32μF+32μF 500V electrolytic filter cap

r (1) 1N4007 1000V rectifier diode

r (1) Cabinet

r (1) Chassis

r (1) Turret board

r (1) Faceplate/backplate set

Resistors

r (1) 470Ω .5W carbon composite

r (2) 820Ω .5W carbon composite

r (2) 5.1K .5W carbon composite

r (1) 10K .5W carbon composite










r (4) 1M .5W carbon composite

r (2) 470Ω 2W metal oxide

r (2) 10K 2W metal oxide

r (1) 1K 5W ceramic

(also called a can capacitor)

250+

8µF

510K47

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32μF

500V

.047μF

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.1μF

250μF

5W 1K

Brown Green Orange Gold

Yellow Violet Orange Gold

Red Violet Yellow Gold

Yellow Violet Brown Gold

Brown Black Orange Gold

Yellow Violet Brown Gold

Gray Red Brown Gold

Green Brown Red Gold

Brown Black Orange Gold

Red Violet Orange Gold

Green Blue Orange Gold

Blue Gray Orange Gold

Gray Red Orange Gold

Brown Black Yellow Gold

Red Red Yellow Gold

Brown Black Green Gold

A magnifier helps!

Parts list


Parts listTubes, lamps, fuses, and sockets

r (1) Two-lug jack

r (5) Four-lug jack

r (3) Nine-pin tube socket

r (3) Shield for nine-pin tube socket

r (3) Eight-pin tube socket

r (3) Tension clip for eight-pin socket

r (3) 12AX7 preamp tube (also called ECC83S)

r (2) EL34 power tube

r (1) 5AR4 rectifier tube (also called GZ34)

r (2) Fuse socket

r (1) Fuse (3 amp, slow blow)

r (1) Fuse (500 milliAmp, fast blow)

r (1) Indicator light

r (1) Power inlet

Control pots and more

r (1) 10KL bias pot

r (3) 1M control pot (A-audio taper)

r (1) 5K control pot (L-linear taper)



r (1) Impedance selector switch

r (7) Knob

r (3) Three-lug terminal strip

r (1) Power switch (2 lugs)

r (1) Standby switch (2 lugs)

Wire

r (1) Black wire

r (1) White wire

r (1) Green wire

r (1) Yellow wire

Heat-shrink tubing

r (3) 1/8” diameter (2-1/2” length)

r (1) 1/16” diameter (2-1/2” length)

Transformers

r (1) Power transformer

r (1) Output transformer

r (1) Filter choke12A

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Vintage-style push-back wire lets you push the insulation back instead of trimming it. BUT: Trimming it still works better!

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25KL

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10KL


#0531 StewMac Solder Monster

#3000 Guitar Tech Screwdriver Set

#1606 Wire Stripper

#1607 Wire Cutter

#0501 Solomon SL-30 Soldering Station

#1609 Round Nose Bending Pliers #0505

Kester Pocket-Pak Solder

StewMac’s Solder Monster holds parts while you solder

Tools and supplies

Required Phillips screwdrivers, #1 and #2 Item #3000 Guitar Tech Screwdriver Set

Needle nose pliers Item #1610 Long Nose Pliers

Wire cutter Item #1607 Wire Cutter

Wire stripper Item #1606 Wire Stripper

Soldering iron (preferably 40W) Item #0501 Solomon SL-30 Soldering Station

Solder (at least one Pocket-Pak) Item #0505 Kester Pocket-Pak Solder

Solder sucker Item #0503 Solomon Solder Sucker

Drill with a 5/32" bit For mounting turret board and filter cap

Ruler Item #4905 StewMac Shop Rule

Digital multimeter Item #3618 Fieldpiece Pocket Multimeter

Snuffer stick (bleed resistor) Item #1552 Snuffer Stick

Pencil Wooden chopsticks Glue Wood glue, white glue, or contact cement for gluing a paper label inside the cabinet

Butane lighter or matches For heating heat-shrink tubing

Contact cement

Helpful Round nose bending pliers Item #1609 Round Nose Bending Pliers

Solder wick Item #0504 Solder Wick, 5-foot roll

Soldering aids Item #0521 StewMac Soldering Aids

Soldering stand Item #0506 Solomon Soldering Stand

Solder Monster, or helping hand tool Item #0531 StewMac Solder Monster

Chassis stand Item #10750 Chassis Stand

Printed circuit board vise Scratch awl or center punch Item #3000 Guitar Tech Screwdriver Set

Tray for loose parts Bias meter for accurate biasing Item #1580 VHT Tube Tester + Amp Bias Meter


High voltage, even when unpluggedWhen you turn on an amp, the capacitors are designed to take on a charge and hold it . That stored voltage is enough to injure you seriously, or even kill you .

These components aren’t a threat until the first time you plug the amp in . The stored electricity can be safely discharged to ground with a snuffer stick . See how to use it below .

Once your amp has been turned on, don’t touch the wiring with your bare hands—even after turning it off . If you need to press on a contact, use a chopstick or Sharpie marker, which are both non-conductive . Don’t use a pencil, because graphite is conductive .

It’s important that you understand the dangers so you’re working safely . Here’s how to do it right .

Wear rubber-soled shoesRubber soles increase the insulation between yourself and the ground .

Take off your ringA metal ring on your finger can bridge a hot connection to ground .

Wear safety glassesRosin-core solder sometimes bubbles up, and it can spew molten specks into the air . You don’t want molten solder in your eyes .

It’s better not to work aloneElectrical shocks can incapacitate you, and having someone available to call 911 can be a lifesaver .

How to use a snuffer stickTo discharge a capacitor, clip the snuffer stick lead to ground—preferably a mounting bolt on the power transformer . Hold the tip of the stick to the cap’s positive lead and use your multimeter to watch the voltage drain to less than 18V .

Take breaks and stop when you’re tiredFatigue leads to mistakes, and no one can afford mistakes when working with electricity .

Stay suspiciousWhether it’s the first time you’ve been inside a live ampli-fier or the 100th time, don’t become complacent . If you discharge the caps and walk away for a few minutes, check again for residual voltage when you return . Capacitors can self-charge through a phenomenon known as dielectric memory .

Check before powering on It’s easy to forget that you a left a stray tool or wire in the chassis . It’s also easy to forget to re-attach the speaker wire, and that can fry an output transformer in seconds . Constant vigilance is your friend when working on amps .

Always unplug itUnplug the amp whenever you don’t specifically need it plugged in . Some points are always hot when the amp’s plugged in, even if the power switch is off . These points include the lugs on the fuse socket, power switch, and standby switch .

Amp voltages are seriously dangerous!

Professionals who work on amps take these safety habits very seriously


A resistor’s value—the amount of resistance it creates—is rated in ohms (Ω) . Larger ohm values mean more resistance . For example, a 100Ω resistor creates ten times as much re-sistance as a 10Ω resistor .

The resistors used in amplifiers are too small to have value numbers printed on them . Instead, a system of colored bands tells their values . The key to reading these bands is provided below . However, an easier way to decode these bands is to download one of the many smartphone apps for this purpose .

One band will be the nearest to an end of the resistor . That band tells the first value . Combine it with the value of band 2 to get a two-digit number (68 in our example below) . Multiply that number by band 3 (68 x 1,000 = 68,000) . Thou-sands are represented by the letter K, so this resistor is 68K (kilo-ohms, or KΩ) .

If there is a fourth band, it will be either silver or gold . This indicates the tolerance allowed during manufacturing . The resistors used in this kit have a +/- 5% tolerance, represented by a gold band 4 .

A magnifying glass helps a lot . The bands on a 470Ω resistor are yellow/violet/brown, and the bands on a 47K resistor are yellow/violet/orange . They’re easily confused!

Can’t read the colors?You can always use a multimeter to test a resistor’s value . Set your meter to ohms and connect the test leads on each side of the resistor .

Capacitor values are typically printed on the component . The key values with caps are their capacitance and voltage .

Think of a capacitor as a container that can hold electricity . Capacitance, measured in farads, refers to how much elec-tricity this container can hold—its capacity . One farad (1F) would be much too large for use in an amplifier . Caps for amps are rated in millionths of a farad, called microfarads (μF), or trillionths of a farad: picofarads (pF) . The voltage spec for a cap refers to how much DC voltage it can handle at any given time .

A unique property of capacitors is that they don’t allow DC current to flow past them, only AC current . This is important in parts of an amplifier circuit, such as the path between a preamp stage and a power amp stage . Here, a “coupling capacitor" will block DC voltage, allowing only the AC guitar signal to pass .

Filter capsCapacitors also filter out 60Hz hum, or “ripple," after the AC current from the wall is converted to DC . These capacitors are called filter caps, because they filter out the ripple from a power supply . The filter caps in this amp are the 32μf + 32μf electrolytic can capacitors . This means that each physical capacitor has two caps inside, each with their own positive lug, and they share a common negative lug .

Electrolytic capsElectrolytic capacitors contain electrolyte: a liquid or gel that gives them a large storage capacity . Electrolytic caps are typically polarized .

Polarized capsSome capacitors have polarity and some don’t . It’s extremely important to install polarized caps correctly in a circuit . The positive lead of an electrolytic cap will be indicated by an indented ring around one edge of the capacitor . The nega-tive lead will often be indicated by a band of arrows pointing to the negative lead .

Installing capacitors with the polarity backwards will make the circuit malfunction and quickly destroy the capacitor—even causing it to explode .

Band 1 Band 2 Band 3 Band 4 1st Digit 2nd Digit Multiplier Tolerance

6 8 x1,000 +/- 5%

68K +/- 5%K = 1,000

Blue

Read this band first (closest to an end)

Gray Orange Gold

BLACK 0 0 1 None +/- 20%

BROWN 1 1 10

RED 2 2 100

ORANGE 3 3 1,000

YELLOW 4 4 10,000

GREEN 5 5 100,000

BLUE 6 6 1,000,000

VIOLET 7 7

GRAY 8 8 0.01 +/- 10% SILVER

WHITE 9 9 0.1 +/- 5% GOLD

NegativePositive

+ 25μF

32μ

F +

32μ

F50

0V

How to read resistor values Capacitor values


V5EL34

V4EL34

POWER STANDBY INDICATORLIGHT

PRESENCE BASS MIDDLE TREBLE HIGH TREBLELOUDNESS 1

NORMALLOUDNESS 2

INPUT 1(HIGH TREBLE)

INPUT 2(NORMAL)

POWER INLETFUSE H.T. FUSE IMPEDANCE

V65AR4

V312AX7

V212AX7

V112AX7

SPEAKER EXTENSIONSPEAKER

-

43

2 1

87

65

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87

65

43

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30 3327

35

29 31 3225

34

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3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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8µF

.022μF

.022μF

.022μF

.1μF

.1μF

.1μF

47

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250μF

.022μF

.022μF

500pF

250

250

Complete wiring diagram

Our diagrams show a flat view of the metal chassis

Here’s the complete Brit-Plex 45 wiringWhen you’ve finished the kit, you’ll have connected all the parts shown in this wiring diagram . If it looks complex now, don’t worry; we’ll start at the very beginning and do this one step at a time .

Your amp-building skills will get stronger with each step!


Start by prepping the turret board

n Wrap the leads tightly for a good electrical contact before soldering . Don’t use solder to “glue" loose joints .

n Melt a small amount of solder onto the tip of the iron (“tinning" the iron) . Hold the tip against the joint for a few seconds, until the connection reaches soldering temperature .

Also tin component leads like multi-strand wires to help the solder flow .

You’re ready to build!

Tips for great soldering!

STEP 1

Number the turretsThe steps refer to the turrets by num-ber . Number the turrets on your board by putting tape along the edges and writing with a fine-point marker . You’ll remove the tape before installing the board .

Leave the turrets in the center of the board (#24–34) unmarked . You can identify these turrets by referring to the diagrams .

n Keep your soldering tip clean by wiping it often on a damp sponge . Keep it tinned by occasionally melting a little solder onto it .

n Feed solder to the connection not to the iron . Keep the iron on the con-nection for a second longer to allow time for all of the flux to cook out of the joint .

n Don’t ever blow on the hot solder or touch anything until the joint is completely cool . A good solder joint is shiny—a sign that it was left to cool undisturbed .

2

1 23

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3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

n Trim away the excess wires after the joint has cooled .

n Plan ahead so each joint is only soldered once . Resoldered joints are messy and more likely to fail .

n Position the parts so their specs face out so you can read them later . Many builders also align resistor bands to read in the same direction .

n How much insulation to strip? With plastic insulation, strip 3/8" from the wire ends . Push-back wire works best when you strip away about 1/4" of the cloth wrap .

Component leads are wrapped onto the turrets and left unsoldered while you add other parts . This way, you can check your work and make correc-tions without having to redo a solder joint . Ideally you solder a turret only once, which is the best way to get clean, trouble-free connections .

When it's time to solder, flow the solder all the way around the turret .

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inal

str

ips

as

pic

ture

d ab

ove .

Cu

t tw

o 1

" p

iece

s o

f g

reen

wir

e an

d re

mov

e th

e in

sula

tion .

Wra

p a

nd s

old

er

one

of th

e w

ires

acro

ss o

ne o

f the

str

ips,

el

ectr

ical

ly c

on

nec

tin

g t

he

thre

e lu

gs .

Th

is w

ill b

e us

ed a

s a

gro

und

ing

str

ip .

Rep

eat

this

pro

cess

wit

h t

he

seco

nd

term

inal

str

ip . Y

ou n

ow h

ave

two,

thre

e-lu

g gr

ound

ing

strip

s .

The

third

term

inal

str

ip w

ill b

e tu

rned

in

to a

tw

o-lu

g gr

ound

ing

strip

, wit

h on

e lu

g le

ft u

ngro

und

ed .

Cut a

3/4

" pie

ce o

f gre

en w

ire a

nd re

mov

e th

e in

sula

tion .

Wra

p a

nd s

old

er th

e w

ire

acro

ss t

wo

nei

gh

bo

rin

g l

ug

s o

n t

his

st

rip . L

eave

the

thi

rd lu

g un

conn

ecte

d .

This

un

con

ne

cte

d l

ug

wil

l b

e u

sed

to t

erm

inat

e an

un

use

d t

ran

sfo

rmer

w

indi

ng .

S

TE

P 4

Inst

all t

hre

e ru

bb

er g

rom

met

sSq

uee

ze t

hes

e in

to t

he

thre

e h

ole

s as

sh

own .

The

se p

rovi

de

stra

in re

lief f

or th

e tr

ansf

orm

er w

ires

that

will

pas

s th

roug

h th

e m

etal

cha

ssis

.

Insi

de

a tr

ansf

orm

er is

a p

rimar

y co

il an

d a

seco

ndar

y co

il . Y

our 1

20V

AC

hou

seho

ld

curr

ent g

oes

into

the

prim

ary

coil

and

is

tran

sfor

med

into

hig

her

volt

age

whi

ch

is o

utp

ut

by

the

seco

nd

ary

coil .

Th

is

volt

age

can

be

as h

igh

as 5

00V,

and

is

refe

rred

to a

s hig

h te

nsio

n (H

.T .) .

The

lead

s co

nnec

ting

to t

hese

tw

o co

ils a

re c

alle

d p

rimar

y an

d se

cond

ary

lead

s .

S

TE

P 5

Mo

un

t th

e p

ow

er t

ran

sfo

rmer

The

pow

er tr

ansf

orm

er h

as tw

elve

lead

s .

Sepa

rate

thes

e in

to c

olor

-cod

ed p

airs

and

tw

ist t

hese

pai

rs to

geth

er:

Tw

o re

d le

ads

Two

gree

n le

ads

Two

yello

w le

ads

Solid

bla

ck a

nd s

trip

ed b

lack

/blu

e

Strip

ed b

lack

/yel

low

and

str

iped

bla

ck/w

hite

Feed

all

the

tran

sfor

mer

lea

ds in

to t

he

chas

sis

thro

ugh

the

squa

re h

ole

with

the

gree

n le

ads

clos

est

to t

he t

ube

sock

ets

and

the

red

lead

s on

the

sam

e si

de

as th

e fr

ont p

anel

con

trol

s .

Inst

all

the

tran

sfo

rmer

on

th

e o

uts

ide

of t

he c

hass

is, u

sing

fou

r 8-

32 lo

cknu

ts

insi

de .

Ad

d t

he t

erm

inal

str

ips

at t

hree

co

rner

s as s

how

n . T

he tw

o-lu

g gr

ound

ing

stri

p g

oes

on t

he b

ack

corn

er n

ear

the

mai

ns

fuse

so

cket

an

d t

he

thre

e-lu

g g

rou

nd

ing

str

ips

sho

uld

be

pla

ced

as

show

n on

the

wiri

ng d

iagr

am .

S

TE

P 6

Mo

un

t th

e o

utp

ut

tran

sfo

rmer

One

sid

e of

the

out

put

tra

nsfo

rmer

has

b

lue,

red

, an

d b

row

n w

ires

. Th

ese

are

the

pri

mar

y le

ads

of

the

tran

sfo

rmer

. P

ass

thes

e th

ree

wir

es t

hro

ug

h t

he

gro

mm

eted

ho

le c

lose

st t

o t

he

fro

nt

pan

el o

f the

cha

ssis

.

The

othe

r sid

e of

the

outp

ut tr

ansf

orm

er

has

oran

ge,

gre

en, y

ello

w, b

row

n, a

nd

bla

ck w

ires

. Th

ese

are

the

seco

nd

ary

lead

s o

f th

e tr

ansf

orm

er .

Twis

t th

e o

ran

ge

+ g

reen

+ y

ello

w s

eco

nd

ary

wire

s to

get

her .

Pass

the

se t

hrou

gh t

he

gro

mm

eted

ho

le c

lose

st t

o t

he

bac

k p

anel

, alo

ng w

ith t

he b

row

n an

d b

lack

w

ires

(five

wire

s th

roug

h th

is g

rom

met

) .

Use

four

8-3

2 x

1/4"

mac

hine

scr

ews

with

lo

ck n

uts t

o m

ount

the

tran

sfor

mer

on

the

outs

ide

of th

e ch

assi

s .

S

TE

P 7

Mo

un

t th

e fi

lter

ch

oke

The

filte

r cho

ke is

a si

ngle

-coi

l tra

nsfo

rmer

, al

so k

now

n a

s an

in

du

cto

r, th

at h

elp

s sm

ooth

out

the

AC

rip

ple

left

ove

r in

the

high

vol

tage

sig

nal .

This

mea

ns th

e fil

ter

cho

ke o

nly

has

tw

o le

ads,

bot

h b

lack

. Tw

ist

thes

e le

ads

tog

eth

er a

nd

thr

ead

them

thr

oug

h t

he

gro

mm

eted

hol

e in

th

e m

iddl

e of

the

chas

sis .

Use

tw

o 8

-32

mac

hin

e s

crew

s an

d lo

cknu

ts to

mou

nt th

e fil

ter c

hoke

out

side

of

the

chas

sis .

3. S

olde

r

1. S

nip

2. W

rap

stew

mac

.co

m

12

©20

19 S

tew

Mac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

250KL

25KL

1MA

5KL

1MA

12

43

12

43

AA BB

12

43

12

43

ST

EP

15

ST

EP

16

12

43

12

43

Enla

rged

tosh

ow d

etai

lM

ount

jack

s ou

tsid

eon

the

fron

t pan

el

AA BB

AA BB

stew

mac

.co

m

13

©20

19

Stew

Mac

S

TE

P 8

Inst

all t

he

thre

e la

rge

tub

e so

cket

s w

ith

sp

rin

g r

etai

ner

sO

rien

t th

ese

eigh

t-p

in t

ube

sock

ets

so

that

pin

1 is

clo

sest

to

the

rear

pan

el o

f th

e ch

assi

s .

Use

4-4

0 x

3/8"

mac

hin

e sc

rew

s an

d lo

cknu

ts t

o m

ount

the

se s

ocke

ts o

n th

e ou

tsid

e of

the

cha

ssis

. Inc

lud

e a

sprin

g re

tain

er o

n th

e b

otto

m o

f ea

ch s

ocke

t to

pro

vid

e su

pp

ort f

or th

ese

thre

e tu

bes

w

hen

they

’re in

stal

led

late

r .

S

TE

P 9

Inst

all t

he

thre

e sm

all t

ub

e so

cket

sPo

sitio

n th

ese

nine

-pin

soc

kets

so

pin

1

is c

lose

st to

the

rear

pan

el o

f the

cha

ssis

. U

se t

wo

4-40

x 1

/4" m

achi

ne s

crew

s an

d lo

cknu

ts t

o m

ount

the

thr

ee r

emai

ning

tu

be

sock

ets .

S

TE

P 1

0

Inst

all t

he

H.T

. fu

se s

ock

etIn

stal

l the

hig

h-t

ensi

on fu

se so

cket

in th

e b

ack

pan

el .

S

TE

P 1

1

Inst

all t

he

po

wer

inp

ut

Inst

all

the

pow

er in

put

wit

h it

s ce

ntra

l gr

ound

lug

faci

ng th

e ch

assi

s op

enin

g .

S

TE

P 1

2

Inst

all t

he

ind

icat

or

lig

ht

Inst

all t

he in

dica

tor l

ight

in th

e fr

ont p

anel

an

d tw

ist t

he t

wo

lead

s to

geth

er .

Co

il th

ese

wir

es t

emp

ora

rily

to

kee

p

them

out

of

your

way

, sin

ce t

hey

won

’t b

e co

nnec

ted

until

late

r .

S

TE

P 1

3

Ad

d t

he

stan

db

y sw

itch

Mo

un

t th

e st

and

by

swit

ch u

sin

g t

he

switc

h m

ount

ing

nut .

Aft

er in

sert

ing

the

switc

h, p

lace

its

was

her o

n th

e th

read

ed

shaf

t bef

ore

addi

ng th

e nu

t .

S

TE

P 14

Inst

all t

he

rem

ain

ing

co

ntr

ol p

ots

Mou

nt th

e co

ntro

l pot

s so

thei

r thr

ee lu

gs

are

faci

ng

th

e ch

assi

s o

pen

ing

. W

hen

w

e re

fer t

o th

ese

lugs

as

left

or r

ight

, it’s

as

sum

ing

you’

re lo

okin

g at

the

pot

from

th

e sa

me

po

int

of

view

as

the

wir

ing

diag

ram

. M

ount

them

as

follo

ws:

Pres

ence

: 5KL

pot

Ba

ss: 1

MA

pot

Mid

dle

(mid

s): 2

5KL

pot

Tr

eble

: 250

KL p

ot

H

igh

Treb

le L

oudn

ess:

1M

A

S

TE

P 1

5

Wir

e th

e n

orm

al c

han

nel

inp

ut

jack

sU

se tw

o 4-

lug

jack

s fo

r the

inp

uts

on th

e n

orm

al c

han

nel

. Fo

r th

ese

step

s, w

e’ll

refe

r to

thes

e in

put

jack

s as

A a

nd B

.

Mo

un

t th

e ja

cks

tem

po

rari

ly o

n t

he

outs

ide

of th

e ch

assi

s, in

thei

r res

pec

tive

hole

s with

thei

r lug

s poi

ntin

g to

war

d th

e in

dica

tor l

ight

.

Mou

ntin

g th

e ja

cks

outs

ide

the

chas

sis

will

hol

d th

em in

pos

ition

and

giv

e yo

u ro

om to

do

the

tric

ky jo

b o

f wiri

ng th

em

up . A

fter

war

d, th

ey’ll

fit n

icel

y in

sid

e th

e ch

assi

s as

a p

re-w

ired

asse

mb

ly .

In b

uild

ing

th

is a

mp

, yo

u’ll

cu

t p

iece

s o

f w

ire

to m

ake

con

nec

tio

ns .

Th

ese

con

nec

tin

g w

ires

are

cal

led

ju

mp

ers,

an

d yo

u’ll

use

a lo

t of

the

m in

bui

ldin

g th

is a

mp .

Cut a

2" l

engt

h of

yel

low

wire

. Rem

ove

the

insu

latio

n to

cre

ate

a b

are

wire

jum

per

.

Bend

a s

mal

l hoo

k on

one

end

and

run

th

e lo

ng s

trai

ght

end

thro

ugh

lug

2 an

d lu

g 3

of ja

ck A

, and

thro

ugh

lug

2 an

d lu

g 3

of ja

ck B

.

Sold

er th

is ju

mp

er to

lug

3 of

jack

A .

S

TE

P 1

6

No

rmal

ch

ann

el ja

cks,

co

nti

nu

ed…

Run

one

lead

of a

1M

resi

stor

thro

ugh

lug

3 of

jack

B a

nd th

e ot

her l

ead

thro

ugh

lug

4 of

jack

B .

Sold

er th

e re

sist

or le

ad a

nd ju

mp

er le

ad

to lu

g 3

of ja

ck B

and

trim

aw

ay a

ny e

xces

s ju

mp

er a

nd re

sist

or le

ad .

Cut a

1" p

iece

of y

ello

w w

ire a

nd re

mov

e th

e in

sula

tio

n .

Ru

n t

his

bar

e ju

mp

er

thro

ugh

lug

1 an

d lu

g 2

of ja

ck B

. Sol

der

th

is ju

mp

er to

bot

h lu

gs .

Cut a

2" y

ello

w ju

mp

er a

nd w

rap

one

end

to

lug

4 of

jack

B . S

old

er th

e ot

her e

nd to

lu

g 1

of ja

ck A

.

Rem

ove

thes

e w

ired

-up

inp

ut ja

cks

and

mou

nt t

hem

in t

he s

ame

hole

s on

the

in

sid

e of

the

chas

sis .

(The

ir lu

gs a

re n

ow

faci

ng a

way

from

the

indi

cato

r lig

ht .)

stew

mac

.co

m

14

©20

19 S

tew

Mac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

1MA

1MA

25KL

250KL

1MA

5KL

12

43

12

43

12

43

12

43

AA BB

.1μF

12

43

12

43

ST

EP

17

ST

EP

18

12

43

12

43

Enla

rged

tosh

ow d

etai

lM

ount

jack

s ou

tsid

eon

the

fron

t pan

el

AA BB

AA BB

stew

mac

.co

m

15

©20

19

Stew

Mac

S

TE

P 1

7

Wir

e th

e h

igh

tre

ble

ch

ann

el in

pu

t ja

cks

Ag

ain,

use

tw

o 4-

lug

jac

ks w

hich

we’

ll re

fer t

o as

A a

nd B

.

As y

ou d

id w

ith th

e no

rmal

cha

nnel

jack

s,

asse

mb

le t

hes

e o

n t

he

ou

tsid

e o

f th

e ch

assi

s w

ith

thei

r lu

gs p

oint

ing

tow

ard

the

indi

cato

r lig

ht .

Cut a

2" l

engt

h of

yel

low

wire

. Rem

ove

the

insu

latio

n to

cre

ate

a b

are

wire

jum

per

.

Bend

a s

mal

l hoo

k on

one

end

and

run

th

e lo

ng s

trai

ght

end

thro

ugh

lug

2 an

d lu

g 3

of ja

ck A

, and

thro

ugh

lug

2 an

d lu

g 3

of ja

ck B

.

Sold

er th

is ju

mp

er to

lug

3 of

jack

A .

S

TE

P 1

8

Hig

h t

reb

le c

han

nel

jack

s,

con

tin

ued

…Ru

n on

e le

ad o

f a 1

M re

sist

or th

roug

h lu

g 3

of ja

ck B

and

the

othe

r lea

d th

roug

h lu

g 4

of ja

ck B

.

Sold

er th

e re

sist

or le

ad a

nd ju

mp

er le

ad

to lu

g 3

of ja

ck B

and

trim

aw

ay a

ny e

xces

s ju

mp

er a

nd re

sist

or le

ad .

Cut a

1" p

iece

of y

ello

w w

ire a

nd re

mov

e th

e in

sula

tio

n .

Ru

n t

his

bar

e ju

mp

er

thro

ugh

lug

1 an

d lu

g 2

of ja

ck B

. Sol

der

th

is ju

mp

er to

bot

h lu

gs .

Cut a

2" y

ello

w ju

mp

er a

nd w

rap

one

end

to

lug

4 of

jack

B . S

old

er th

e ot

her e

nd to

lu

g 1

of ja

ck A

.

Rem

ove

thes

e w

ired

-up

inp

ut ja

cks

and

mou

nt t

hem

in t

he s

ame

hole

s on

the

in

sid

e of

the

chas

sis .

(The

ir lu

gs a

re n

ow

faci

ng a

way

from

the

indi

cato

r lig

ht .)

S

TE

P 19

Ad

d t

wo

gro

un

d ju

mp

ers

Cut

one

1-3/

4" g

reen

jum

per

and

wra

p

on

e en

d t

o l

ug

2 o

f th

e h

igh

tre

ble

ch

anne

l jac

k A

. Sol

der

the

oth

er e

nd t

o lu

g 2

of th

e no

rmal

cha

nnel

jack

A .

Cut a

3" g

reen

jum

per

and

wra

p o

ne e

nd

to lu

g 2

of th

e hi

gh tr

eble

cha

nnel

jack

A .

Sold

er th

is ju

mp

er e

nd in

pla

ce w

ith th

e tw

o ot

her

jum

per

s al

read

y th

ere .

Tur

n th

e no

rmal

cha

nnel

loud

ness

pot

sha

ft

cloc

kwis

e to

its

zero

pos

ition

and

sol

der

th

e ot

her e

nd o

f thi

s ju

mp

er to

the

bac

k of

the

norm

al c

hann

el lo

udne

ss p

ot .

S

TE

P 2

0

Gro

un

d t

hre

e co

ntr

ol p

ots

Turn

all

pot

sha

fts

coun

terc

lock

wis

e to

th

eir

zero

pos

itio

n b

efor

e st

arti

ng

thi

s st

ep . T

his

is b

ecau

se y

ou’ll

be

app

lyin

g he

at to

thei

r cas

es, a

nd if

the

heat

ling

ers

too

long

it c

ould

cre

ate

an im

pre

ssio

n on

th

e w

iper

insi

de . T

his i

sn’t

a co

ncer

n if

the

pot

is in

the

zero

pos

ition

.

Cut

thre

e 1"

jum

per

s of

gre

en w

ire, p

ull

off th

eir i

nsul

atio

n, a

nd b

end

one

end

of

each

in to

a h

ook .

Star

tin

g w

ith

th

e n

orm

al c

han

ne

l lo

udne

ss p

ot s

old

er th

e ho

ok e

nd o

f the

ju

mp

er t

o th

e le

ft lu

g of

the

pot

. Sol

der

th

e st

raig

ht e

nd

of

this

jum

per

to

the

bac

k of

the

pot

.

Rep

eat

this

pro

cess

for

the

hig

h tr

eble

lo

udne

ss p

ot a

nd th

e m

ids

pot

.

S

TE

P 2

1

Ad

d t

wo

yel

low

jum

per

sC

ut

a 4"

yel

low

ju

mp

er .

Stri

p 3

/4"

of

insu

latio

n fr

om o

ne si

de . R

un th

is ju

mp

er

dow

n th

roug

h th

e m

iddl

e lu

g of

the

bas

s p

ot a

nd b

ack

up th

roug

h th

e rig

ht lu

g of

th

e b

ass

pot

. Sol

der

this

jum

per

to b

oth

lugs

of t

he b

ass

pot

. Rou

te th

e ot

her e

nd

of th

is ju

mp

er o

ver t

he m

ids p

ot a

nd w

rap

th

e ot

her e

nd th

roug

h th

e le

ft lu

g of

the

treb

le p

ot . D

on't

sold

er th

is e

nd y

et .

Cut a

3-1

/4" y

ello

w ju

mp

er a

nd so

lder

one

en

d to

the

left

lug

of th

e b

ass

pot

. Sol

der

th

e ot

her e

nd o

f thi

s ju

mp

er to

the

right

lu

g of

the

mid

s p

ot .

S

TE

P 2

2

Ad

d a

.1μ

F ca

pac

ito

rSo

lder

a .1

μF c

ap b

etw

een

the

left

lug

of

the

pre

senc

e p

ot a

nd t

he m

iddl

e lu

g of

th

e sa

me

pot

. Ben

d t

he c

apac

itor

lea

d fr

om t

he le

ft lu

g of

the

pot

to

the

bac

k of

the

pot

and

sol

der

it . T

rim a

way

any

ex

cess

lea

d a

t th

e m

idd

le l

ug

an

d t

he

bac

k of

the

pot

.

stew

mac

.co

m

16

©20

19 S

tew

Mac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

12

43

12

43

12

43

12

43

stew

mac

.co

m

17

©20

19

Stew

Mac

S

TE

P 2

3

Po

wer

tra

nsf

orm

er r

ed le

ads

Run

the

two

red

wire

s fr

om t

he p

ower

tr

ansf

orm

er t

o t

he

V6

rect

ifie

r tu

be

sock

et . T

rim

the

se w

ires

to

leng

th a

nd

sold

er o

ne t

o p

in 4

and

the

oth

er t

o p

in

6 . E

ither

wire

can

go

to e

ither

lug .

S

TE

P 2

4

Po

wer

tra

nsf

orm

er y

ello

w le

ads

Run

the

two

yello

w w

ires f

rom

the

pow

er

tran

sfo

rmer

to

th

e V

6 re

ctif

ier

tub

e so

cket

. Tri

m t

hese

wir

es t

o le

ngth

an

d so

lder

one

to

pin

2 a

nd t

he o

ther

to

pin

8 .

Eith

er w

ire c

an g

o to

eith

er lu

g

S

TE

P 2

5

Po

wer

tra

nsf

orm

er b

lack

an

d b

lack

/b

lue

lead

sRu

n th

e tw

iste

d p

air

of s

olid

bla

ck a

nd

stri

ped

bla

ck/b

lue

pow

er t

ran

sfo

rmer

le

ads

to th

e m

ains

fuse

soc

ket a

nd w

rap

th

em b

oth

to t

he le

ft lu

g . D

on't

sold

er

them

yet

.

S

TE

P 2

6

Po

wer

tra

nsf

orm

er b

lack

/yel

low

an

d b

lack

/wh

ite

lead

sRu

n t

he

twis

ted

pai

r of

str

iped

bla

ck/

yello

w a

nd

str

iped

bla

ck/w

hit

e p

ower

tr

ansf

orm

er le

ads

to t

he r

ight

lug

of t

he

pow

er s

witc

h an

d w

rap

the

m o

n to

the

lu

g . D

on't

sold

er th

em y

et .

S

TE

P 2

7

Po

wer

tra

nsf

orm

er r

ed/y

ello

w le

adR

un

th

e s

trip

ed

re

d/y

ell

ow

po

we

r tr

ansf

orm

er le

ad t

o th

e H

.T . f

use

sock

et,

cut i

t to

an a

ppro

pria

te le

ngth

, and

sold

er

it to

the

left

lug .

S

TE

P 2

8

Po

wer

tra

nsf

orm

er g

reen

/yel

low

le

adR

un

th

e st

rip

ed g

reen

/yel

low

po

wer

tr

an

sfo

rme

r le

ad

to

th

e t

wo

-lu

g g

rou

nd

ing

str

ip n

ext

to

th

e m

ain

s fu

se s

ock

et a

nd

sol

der

it

to t

he

cent

er

grou

ndin

g lu

g as

sho

wn .

S

TE

P 2

9

Inst

all o

ne

pil

ot-

lig

ht

lead

Cut

eith

er o

ne o

f the

pilo

t lig

ht le

ads

to

an a

pp

rop

riat

e le

ng

th a

nd

sol

der

it

to

the

right

lug

of t

he p

ower

sw

itch

alon

g w

ith th

e st

riped

bla

ck/y

ello

w a

nd st

riped

b

lack

/whi

te p

ower

tran

sfor

mer

lead

s .

S

TE

P 3

0

Inst

all t

he

oth

er p

ilo

t-li

gh

t le

adCu

t a

5" y

ello

w ju

mp

er to

be

conn

ecte

d to

the

othe

r pilo

t lig

ht le

ad . S

trip

3/4

" of

in

sula

tion

back

from

bot

h th

e ju

mp

er a

nd

the

pilo

t la

mp

lead

, tw

ist

the

bar

e w

ires

toge

ther

, and

sol

der

them

.

Slid

e 1"

of

1/8"

hea

t-sh

rink

tub

ing

over

th

e so

lder

join

t an

d ad

d he

at t

o cr

eate

el

ectr

ical

insu

lati

on o

ver

the

bar

e w

ire

of th

ese

sold

ered

lead

s .

Sold

er th

e fr

ee e

nd o

f thi

s ju

mp

er to

the

left

lug

of t

he m

ains

fus

e so

cket

alo

ng

with

the

pow

er tr

ansf

orm

er le

ads a

lread

y w

rap

ped

in p

lace

.

Use a

match

or lig

hter

to ins

ulate

wires

with

heat-s

hrink

tubing

stew

mac

.co

m

18

©20

19 S

tew

Mac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

4 3

21

87

65

4 3

21

87

65

12

43

12

43

12

43

12

43

stew

mac

.co

m

19

©20

19

Stew

Mac

S

TE

P 3

1

Ad

d t

wo

yel

low

jum

per

sCu

t one

14"

yel

low

jum

per

and

sold

er o

ne

end

to t

he r

ight

lug

of t

he p

ower

inp

ut .

Run

the

othe

r end

of t

his

jum

per

aro

und

the

outs

ide

wal

l of t

he c

hass

is a

nd so

lder

it

to th

e le

ft lu

g of

the

pow

er s

witc

h .

Cut o

ne 4

" jum

per

and

sol

der

one

end

to

the

left

lug

of th

e p

ower

inp

ut . S

olde

r the

ot

her

end

to t

he r

ight

lug

of t

he m

ains

fu

se s

ocke

t .

S

TE

P 3

2

Ad

d o

ne

gre

en ju

mp

erCu

t on

e 3-

1/4"

gre

en ju

mp

er a

nd s

old

er

one

end

in to

the

mid

dle

lug

of th

e p

ower

in

put

. Sol

der

the

othe

r end

to th

e le

ft lu

g of

the

two

-lug

grou

ndin

g st

rip c

lose

st to

th

e m

ains

fuse

soc

ket .

S

TE

P 3

3

Inst

all t

he

bia

s p

ot

Mou

nt t

he 1

0KL

bia

s p

ot in

the

floo

r of

th

e ch

assi

s as

sho

wn .

S

TE

P 3

4

Gro

un

d t

he

po

wer

tu

be

sock

ets

Cut

tw

o 3/

4" g

reen

jum

per

s an

d b

end

them

bo

th i

nto

a U

sh

ape .

Ad

d o

ne

jum

per

bet

wee

n V

5 p

in 1

an

d p

in 8

. So

lder

th

is j

um

per

to

pin

1 .

Ad

d t

he

othe

r ju

mp

er b

etw

een

V4 p

in 1

and

pin

8 .

Sol

der

this

jum

per

to p

in 8

.

Cut a

4" g

reen

jum

per

. Sol

der

one

end

to

V4 p

in 1

alo

ng w

ith t

he ju

mp

er in

pla

ce

and

wra

p th

e ot

her e

nd to

V5

pin

8 .

Cut a

3" g

reen

jum

per

and

sold

er o

ne e

nd

to V

5 p

in 8

with

the

oth

er t

wo

jum

per

s .

Sold

er th

e ot

her e

nd o

f thi

s jum

per

to o

ne

of th

e lu

gs o

n th

e ne

arby

gro

undi

ng st

rip .

S

TE

P 3

5

Ad

d t

wo

470

Ω 2

W r

esis

tors

Thes

e re

sist

ors

pro

tect

the

pow

er t

ubes

an

d t

he

ou

tpu

t tr

ansf

orm

er,

and

in

doi

ng th

is c

an g

et e

xtre

mel

y ho

t . Fo

r thi

s re

ason

, the

y ne

ed to

be

mou

nted

up

and

aw

ay fr

om th

e tu

be

sock

ets

by 1

/2” .

Wra

p o

ne

lead

of

the

firs

t 47

0 Ω

2W

re

sist

or to

pin

4 o

f V5

and

wra

p th

e ot

her

lead

to p

in 6

of V

5, s

tand

ing

it up

off

the

tub

e so

cket

1/2

" . So

lder

the

lead

wra

pped

to

pin

4 .

Wra

p o

ne

lead

of

the

seco

nd

470

Ω

resi

stor

to p

in 4

of V

4 an

d w

rap

the

othe

r le

ad to

pin

6 o

f V4,

sta

ndin

g it

up o

ff th

e tu

be

sock

et 1

/2" .

Sold

er th

e le

ad w

rapp

ed

to p

in 4

.

S

TE

P 3

6

Ad

d o

ne

yell

ow

jum

per

Cut o

ne 4

" yel

low

jum

per

. Sol

der o

ne e

nd

of th

e ju

mp

er to

V5

pin

6 w

ith th

e re

sist

or

lead

alre

ady

in p

lace

. Wra

p th

e ot

her e

nd

to V

4 p

in 6

, but

don

't so

lder

it y

et .

stew

mac

.co

m

20

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

4 3

21

87

65

4 3

21

87

65

12

43

12

43

12

43

12

43

stew

mac

.co

m

21

©

2019

St

ewM

ac

S

TE

P 3

7

Inst

all t

he

hea

ter

wir

esTu

bes

requ

ire a

6 .3

V A

C c

urre

nt to

pow

er

thei

r fi

lam

ents

, w

hic

h a

re a

lso

cal

led

"hea

ters

" in

the

am

p w

orld

. Thi

s cu

rren

t is

pro

vid

ed b

y th

e p

ower

tra

nsf

orm

er

thro

ugh

the

gree

n le

ads .

The

Briti

sh st

yle

of ru

nnin

g he

ater

wire

s is

to tu

ck th

em in

to th

e b

otto

m b

ack

corn

er

of t

he c

hass

is . K

eep

ing

the

wire

s tu

cked

in

to th

e b

ack

corn

er o

f the

cha

ssis

, aw

ay

from

the

sig

nal c

arry

ing

wire

s, p

reve

nts

the

AC

cur

rent

in th

ese

heat

er w

ires f

rom

b

leed

ing

60hz

hum

into

you

r sig

nal .

S

TE

P 3

8

Co

nn

ect

to s

ock

et V

5Ru

n th

e p

ower

tra

nsfo

rmer

gre

en w

ires

to so

cket

V5,

kee

ping

them

dow

n as

clo

se

to th

e ch

assi

s as

pos

sib

le .

Cut

two

8" h

eate

r w

ires,

one

whi

te a

nd

on

e b

lack

. Tw

ist

them

to

get

her

ver

y ti

gh

tly,

lea

vin

g a

bo

ut

1" o

f th

e en

ds

un

twis

ted

. Jo

in t

he

wh

ite

jum

per

to

eith

er o

f the

gre

en p

ower

supp

ly le

ads b

y tw

istin

g th

e en

ds to

geth

er . J

oin

the

bla

ck

jum

per

to th

e ot

her g

reen

lead

.

Sold

er t

he

pai

r w

ith

th

e w

hite

wir

e to

p

in 2

of

sock

et V

5 . S

old

er t

he p

air

with

th

e b

lack

wire

to p

in 7

of s

ocke

t V5 .

Ben

d th

ese

wire

s in

to t

he b

ack

corn

er o

f th

e ch

assi

s an

d t

hen

ben

d t

he

bla

ck-a

nd

-w

hite

pai

r at a

90°

ang

le to

war

d so

cket

V4 .

S

TE

P 3

9

Co

nn

ect

to s

ock

et V

4Cu

t tw

o 7"

hea

ter

wire

s, o

ne w

hite

and

on

e b

lack

. Tw

ist t

hem

tigh

tly

toge

ther

.

Twis

t th

e en

d o

f th

e w

hite

wir

e to

th

e w

hite

jum

per

com

ing

from

V5 .

Tw

ist t

he

bla

ck w

ire w

ith th

e b

lack

jum

per

com

ing

from

V5 .

Sold

er t

he w

hite

pai

r on

to p

in 2

of

V4 .

Sold

er th

e b

lack

pai

r ont

o p

in 7

. Ben

d th

e w

ires

into

the

bac

k co

rner

of t

he c

hass

is,

and

on to

war

d so

cket

V3 .

Sold

er th

e w

hite

pai

r to

pin

2 of

sock

et V

4 .

Sold

er th

e b

lack

pai

r to

pin

7 o

f soc

ket V

4 .

Bend

thes

e w

ires

into

the

bac

k co

rner

of

the

chas

sis a

nd th

en b

end

the

bla

ck-a

nd-

whi

te p

air a

t a 9

0° a

ngle

tow

ard

sock

et V

3 .

Use t

his he

ater-w

ire tec

hnique

to

minimi

ze the

hum c

aused

by AC

voltag

eTh

e tw

iste

d gr

een

wire

s fro

m th

e p

ower

tran

sfor

mer

car

ry A

C v

olta

ge to

th

e he

atin

g fil

amen

ts in

the

tub

es . T

his

volt

age

will

cau

se y

our a

mp

to

hum

if th

ese

wire

s are

allo

wed

to ru

n to

o cl

ose

to si

gnal

-car

ryin

g w

ires .

Twis

t th

e w

ires

tig

htl

y to

get

her

This

tw

ist

isn’

t fo

r lo

oks;

it’s

an

imp

orta

nt h

um-c

ance

lling

tec

hniq

ue

to r

educ

e no

ise

in y

our

amp .

It w

orks

in a

way

sim

ilar

to t

he o

pp

o-

site

-wou

nd c

oils

in a

hum

buc

king

pic

kup .

Ro

ute

th

em a

way

To k

eep

tw

iste

d he

ater

wire

s aw

ay f

rom

sig

nal-

carr

ying

wire

s, r

oute

th

em in

to th

e b

ack

edge

of t

he fl

oor o

f the

cha

ssis

. Giv

e th

em a

sha

rp

right

ang

le b

end

tow

ard

the

next

sock

et a

nd a

noth

er sh

arp

ben

d b

ack

dow

n to

tha

t so

cket

. Thi

s ke

eps

them

shi

eld

ed a

nd a

way

from

sig

nal

carr

ying

wire

s .

stew

mac

.co

m

22

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

12

43

12

43

12

43

12

43

stew

mac

.co

m

23

©

2019

St

ewM

ac

S

TE

P 4

0

Co

nn

ect

to s

ock

et V

3O

n so

cket

s V3

, V2,

and

V1

you

will

nee

d to

join

pin

s 4

and

5 to

geth

er . O

n th

ese

thre

e so

cket

s, g

entl

y tw

ist

pin

s 4

and

pin

5 t

owar

d ea

ch o

ther

so

thei

r ey

elet

s lin

e up

. Be

very

car

eful

whi

le d

oing

thi

s as

thes

e p

ins

are

del

icat

e .

Cut

two

7" h

eate

r w

ires,

one

whi

te a

nd

one

bla

ck . T

wis

t the

m ti

ghtl

y to

geth

er .

Twis

t the

end

of t

he w

hite

wire

toge

ther

w

ith t

he w

hite

jum

per

com

ing

from

V4 .

Tw

ist t

he b

lack

wire

with

the

blac

k ju

mp

er

com

ing

from

V4 .

Sold

er t

he w

hite

pai

r to

com

bin

ed p

ins

4+5

on V

3 an

d so

lder

the

bla

ck p

air t

o V3

pi

n 9 .

Ben

d th

e w

ires i

n to

the

bac

k co

rner

of

the

chas

sis,

and

on

tow

ard

sock

et V

2 .

S

TE

P 4

1

Co

nn

ect

to s

ock

et V

2Cu

t tw

o 7"

hea

ter

wire

s, o

ne w

hite

and

on

e b

lack

. Tw

ist t

hem

tigh

tly

toge

ther

.

Twis

t the

end

of t

he w

hite

wire

toge

ther

w

ith t

he w

hite

jum

per

com

ing

from

V3 .

Tw

ist t

he b

lack

wire

with

the

blac

k ju

mp

er

com

ing

from

V3 .

Sold

er t

he w

hite

pai

r to

com

bin

ed p

ins

4+5

on V

2 an

d so

lder

the

bla

ck p

air t

o V2

pi

n 9 .

Ben

d th

e w

ires i

n to

the

bac

k co

rner

of

the

chas

sis,

and

on

tow

ard

sock

et V

1 .

S

TE

P 4

2

Co

nn

ect

to s

ock

et V

1Ru

n th

e bl

ack-

and-

whi

te tw

iste

d pa

ir in

to

the

bac

k co

rner

of t

he c

hass

is a

nd to

war

d V1

. Sol

der

the

bla

ck w

ire to

V1

pin

9 a

nd

sold

er th

e w

hite

wire

to V

1 p

in 4

+5 .

Car

eful

ly in

spec

t ea

ch s

old

er jo

int

from

th

is h

eate

r w

ire

inst

alla

tio

n a

nd

on

ce

the

sold

er jo

ints

hav

e co

oled

pus

h yo

ur

heat

er w

ires

in to

the

floor

of t

he c

hass

is

and

in t

o th

e b

ack

corn

er o

f th

e ch

assi

s as

muc

h as

you

can

.

S

TE

P 4

3

Co

nn

ect

the

ou

tpu

t tr

ansf

orm

er's

b

lue

lead

Rout

e th

e b

lue

outp

ut t

rans

form

er le

ad

as s

how

n on

the

wiri

ng d

iagr

am, a

long

th

e flo

or o

f th

e ch

assi

s, t

o p

in 3

of

the

V5 s

ocke

t . Ro

ute

it lik

e th

is b

ecau

se it

is

a si

gnal

car

ryin

g w

ire a

nd n

eeds

to

be

kep

t aw

ay f

rom

the

hea

ter

wire

s . C

ut it

to

an

ap

pro

pri

ate

len

gth

an

d s

old

er i

t to

V5

pin

3 .

S

TE

P 4

4

Co

nn

ect

the

ou

tpu

t tr

ansf

orm

er's

p

rim

ary

bro

wn

lead

Fin

d t

he

bro

wn

ou

tpu

t tr

ansf

orm

er

lea

d t

hat

is

com

ing

th

rou

gh

th

e sa

me

gro

mm

eted

ho

le a

s th

e o

utp

ut

tran

sfor

mer

blu

e an

d re

d le

ads .

Run

this

b

row

n ou

tput

tran

sfor

mer

lead

as s

how

n on

the

wiri

ng d

iagr

am, a

long

the

floor

of

the

chas

sis,

to p

in 3

of t

he V

4 so

cket

. Cut

it

to a

n ap

pro

pria

te le

ngth

and

sol

der

it

to V

4 p

in 3

.

stew

mac

.co

m

24

©20

19 S

tew

Mac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

1

23

4

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

12

43

12

43

12

43

12

43

stew

mac

.co

m

25

©

2019

St

ewM

ac

S

TE

P 4

5

Term

inat

e th

e o

utp

ut

tran

sfo

rmer

's

seco

nd

ary

bro

wn

lead

Fin

d t

he

bro

wn

ou

tpu

t tr

ansf

orm

er

lea

d t

hat

is

com

ing

th

rou

gh

th

e sa

me

gro

mm

eted

ho

le a

s th

e o

utp

ut

tran

sfor

mer

's y

ello

w, o

rang

e, g

reen

, and

b

lack

lead

s . R

un t

his

bro

wn

lead

to

the

two

-lug

grou

ndin

g st

rip n

ear

the

mai

ns

fuse

soc

ket .

Rout

e th

is le

ad a

s sh

own

on

the

wiri

ng d

iagr

am .

Sold

er th

is b

row

n le

ad to

the

unco

nnec

ted

lug

of th

is s

trip

. Thi

s is

an

unus

ed o

utp

ut

tran

sfor

mer

lead

, whi

ch w

ill c

arry

unu

sed

volt

age .

It n

eeds

to b

e sa

fely

term

inat

ed

and

in

sula

ted

. O

nce

yo

ur

sold

er j

oin

t co

ols,

cov

er it

with

1/2

" len

gth

of 1

/8" h

eat

shrin

k tu

bin

g . A

s the

hea

t shr

ink

tub

ing

is

cool

ing,

pin

ch th

e to

p o

f it w

ith p

liers

to

secu

re th

e so

lder

join

t, sa

fely

term

inat

ing

this

lead

.

S

TE

P 4

6

Ou

tpu

t tr

ansf

orm

er r

ed le

ad +

filt

er

cho

ke le

adTw

ist

the

outp

ut t

rans

form

er's

red

lead

w

ith e

ither

one

of t

he b

lack

filte

r ch

oke

lead

s . R

un t

hese

lead

s to

the

left

lug

of

the

stan

dby

switc

h an

d cu

t th

em t

o an

ap

pro

pria

te le

ngth

. Sol

der

the

m t

o th

e le

ft lu

g of

the

stan

dby

switc

h .

S

TE

P 4

7

Gro

un

d t

he

ou

tpu

t tr

ansf

orm

er's

b

lack

lead

Ru

n t

he

bla

ck w

ire

fro

m t

he

ou

tpu

t tr

ansf

orm

er to

the

3-lu

g gr

ound

ing

strip

ne

ar V

5 . T

rim it

to le

ngth

and

sol

der

it to

th

e rig

ht lu

g of

the

strip

.

S

TE

P 4

8

Ad

d o

ne

gre

en ju

mp

erCu

t one

2" g

reen

jum

per

. Sol

der

one

end

of

this

jum

per

to th

e rig

ht lu

g of

the

H .T

. fu

se s

ocke

t . So

lder

the

oth

er e

nd o

f thi

s ju

mp

er t

o th

e le

ft lu

g of

the

gro

undi

ng

strip

nex

t to

V5 .

S

TE

P 4

9

Ad

d t

wo

yel

low

jum

per

sCu

t tw

o 1"

yel

low

jum

per

s .

Use

one

to

conn

ect

pin

3 a

nd p

in 8

of

sock

et V

1 . S

old

er it

to p

in 3

onl

y .

Use

the

othe

r to

conn

ect p

in 3

and

pin

8

of s

ocke

t V3 .

Sol

der

it to

pin

3 o

nly .

S

TE

P 5

0

Ad

d t

wo

mo

re y

ello

w ju

mp

ers

Cut t

wo

7" y

ello

w ju

mp

ers .

Sold

er o

ne ju

mp

er to

V6

pin

6 a

nd ro

ute

it un

der

the

grou

ndin

g st

rip n

ear V

5 an

d to

war

d t

he

gro

mm

eted

ho

le w

ith

th

e re

d, b

lue,

and

bro

wn

outp

ut tr

ansf

orm

er

lead

s . L

eave

it

ther

e fo

r n

ow, y

ou'll

be

conn

ectin

g it

to th

e tu

rret

boa

rd la

ter .

Sold

er t

he o

ther

jum

per

to

pin

8 o

f V6

an

d r

ou

te i

t b

etw

een

th

e si

de

wal

l o

f th

e ch

assi

s an

d t

he p

ower

tra

nsfo

rmer

to

war

d th

e p

ower

sw

itch .

Lea

ve th

is o

ne

here

for n

ow, t

oo . Y

ou'll

be

conn

ectin

g it

to a

filte

r cap

sho

rtly

.

S

TE

P 5

1

Ad

d a

yel

low

jum

per

+ o

ne

resi

sto

rCu

t one

2" y

ello

w ju

mp

er . S

olde

r one

end

to

V2

pin

7 . R

oute

the

jum

per

aro

und

the

outs

ide

of th

e so

cket

and

wra

p th

e ot

her

end

to p

in 1

of t

he s

ame

sock

et .

Ad

d a

100k

res

isto

r b

etw

een

pin

1 a

nd

pin

6 o

f soc

ket V

2 . S

olde

r the

resi

stor

lead

to

pin

1 a

long

with

the

jum

per

alre

ady

in

pla

ce . L

eave

the

oth

er e

nd u

nsol

der

ed .

Trim

any

exc

ess

lead

.

S

TE

P 5

2

Inst

all t

he

imp

edan

ce s

wit

chM

ount

th

e im

ped

ance

sel

ecto

r sw

itch

as

sho

wn

in t

he d

iagr

am, w

ith t

he t

wo

mid

dle

lugs

faci

ng u

p .

Ther

e is

no

ho

le i

n t

he

chas

sis

for

the

tang

was

her

incl

uded

wit

h th

is s

witc

h,

so s

imp

ly fl

ip t

he w

ashe

r so

the

tan

g is

fa

cing

aw

ay fr

om th

e ch

assi

s w

all .

S

TE

P 5

3

Co

nn

ect

the

imp

edan

ce s

wit

chTh

e im

ped

ance

sel

ecto

r sw

itch

allo

ws

you

to se

t the

am

plifi

er’s

outp

ut to

mat

ch

the

spea

ker c

abin

et y

ou w

ill u

se .

Cu

t th

e o

utp

ut

tran

sfo

rmer

’s t

wis

ted

oran

ge, g

reen

, and

yel

low

wire

s to

leng

th

for c

onne

ctin

g to

the

imp

edan

ce se

lect

or

switc

h .

Sold

er t

he o

rang

e w

ire t

o th

e rig

ht lu

g (lu

g 1

in t

he d

iagr

am) .

Sold

er t

he g

reen

w

ire t

o lu

g 2,

and

the

yel

low

wire

to

lug

3 . T

he le

ft lu

g (4

) is

emp

ty a

t thi

s p

oint

.

1. S

olde

r2.

Cov

er w

ithhe

at-s

hrin

k tu

bin

g3.

Hea

t and

fo

ld o

ver

stew

mac

.co

m

26

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

D C

-

B A

-

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

12

43

12

43

12

43

12

43

.047μF

stew

mac

.co

m

27

©20

19

Stew

Mac

S

TE

P 5

4

Mo

un

t th

e fi

lter

cap

sTh

e fi

lter

cap

acit

ors

are

hel

d t

o t

he

chas

sis

wit

h m

ou

nti

ng

cla

mp

s . T

hes

e cl

amps

att

ach

to th

e ca

pac

itor o

n th

e en

d op

pos

ite th

e lu

gs, a

nd a

re th

en m

ount

ed

to t

he c

hass

is u

sing

6-3

2 x

1/2"

scr

ews

and

nuts

. Pos

ition

the

cla

mp

so

you

can

mou

nt t

he

cap

acit

or’s

neg

ativ

e (–

) lu

g fa

cing

up .

The

tab

s o

n t

he

filt

er c

ap m

ou

nti

ng

clam

ps

will

stic

k ou

t ab

ove

the

edge

of

the

chas

sis .

Use

nee

dle

nos

e p

liers

to

ben

d th

em d

own

so th

ey a

re n

ot st

icki

ng

up a

bov

e th

e ed

ge o

f the

cha

ssis

.

Thes

e tw

o fil

ter

cap

s w

ill b

e re

ferr

ed t

o as

the

fron

t fil

ter

cap

and

the

bac

k fil

ter

cap,

and

thei

r pos

itive

lugs

are

ass

igne

d th

e le

tter

s A

-D fo

r cla

rity .

S

TE

P 5

5

Gro

un

d t

he

filt

er c

aps

Cut

a 2

-1/2

" g

reen

jum

per

. So

lder

on

e en

d of

this

jum

per

to th

e b

ack

filte

r cap

's

nega

tive

(-) lu

g . W

rap

the

othe

r end

of t

his

jum

per

to

the

fron

t fil

ter

cap'

s ne

gativ

e lu

g b

ut d

on't

sold

er it

yet

.

Cut a

4" g

reen

jum

per

. Sol

der

one

end

of

this

jum

per

to

fron

t fil

ter

cap'

s ne

gativ

e lu

g . S

old

er t

he o

ther

end

of t

he ju

mp

er

to o

ne o

f the

lugs

of t

he g

roun

ding

str

ip

und

er th

e p

rese

nce

pot

.

S

TE

P 5

6

Co

nn

ect

on

e ju

mp

erFi

nd th

e 7"

yel

low

jum

per

att

ache

d to

pin

8

of s

ocke

t V6 .

Wra

p th

e fr

ee e

nd o

f tha

t ju

mp

er to

lug

D o

n th

e fr

ont fi

lter c

ap b

ut

don

’t so

lder

it y

et .

S

TE

P 5

7

Ad

d o

ne

jum

per

Cut o

ne 1

-3/4

" yel

low

jum

per

and

sol

der

on

e en

d to

lug

D o

f th

e fr

ont

filte

r ca

p

alon

g w

ith th

e ju

mp

er a

lread

y w

rap

ped

to

tha

t lu

g . W

rap

the

oth

er e

nd o

f th

is

jum

per

to ri

ght l

ug o

f the

stan

dby

switc

h b

ut d

on't

sold

er it

yet

.

S

TE

P 5

8

Ad

d o

ne

cap

Add

1" o

f 1/1

6" h

eat-

shrin

k tu

bin

g to

eac

h le

ad o

f a .0

47μF

cap

acito

r . A

pp

ly h

eat t

o sh

rink

the

tub

ing

to th

e le

ad . S

old

er o

ne

lead

to th

e rig

ht lu

g of

the

stan

dby

switc

h al

ong

with

the

jum

per

alre

ady

in p

lace

. So

lder

the

othe

r lea

d of

this

cap

acito

r to

the

grou

ndin

g st

rip u

nder

the

pre

senc

e p

ot .

Sto

p a

nd

insp

ect

you

r w

ork

This

is a

goo

d tim

e to

ste

p a

way

from

the

pro

ject

for

a f

ew m

inut

es . T

ake

a b

reak

b

efor

e re

view

ing

your

wor

k fo

r err

ors .

Whe

n yo

u’re

read

y to

go

at it

aga

in, v

ery

care

fully

wal

k th

roug

h ev

ery

conn

ectio

n yo

u’v

e m

ade

so f

ar . W

hen

eve

ryth

ing

chec

ks o

ut, y

ou’re

rea

dy

to m

ove

on t

o th

e tu

rret

boa

rd .

STOP

Be sus

piciou

s The

re's a

mistak

e, and

you’re

gonna

find it!

stew

mac

.co

m

28

©

2019

Ste

wM

ac

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

250μF

.022μF

.022μF

500pF

250

stew

mac

.co

m

29

©20

19

Stew

Mac

Wra

pp

ing

par

ts o

nto

th

e tu

rret

bo

ard

You

’re r

ead

y to

sta

rt p

utt

ing

par

ts o

n th

e tu

rret

bo

ard

. In

th

ese

step

s, y

ou’ll

w

rap

the

lead

s on

to t

he t

urre

ts w

ithou

t so

lder

ing,

and

the

sol

der

will

be

add

ed

late

r . Th

is a

llow

s yo

u to

che

ck y

our w

ork

and

mak

e co

rrec

tio

ns

wit

ho

ut

hav

ing

to u

ndo

sold

er jo

ints

. Id

eally

, you

sol

der

ea

ch jo

int o

nly

once

.

S

TE

P 5

9

Wra

p a

n 8

20Ω

res

isto

rW

rap

an

820Ω

res

isto

r b

etw

een

turr

ets

23 a

nd 5

2 .

S

TE

P 6

0

Ad

d a

250

μF

bip

ola

r el

ectr

oly

tic

cap

acit

or

+ t

wo

jum

per

sN

orm

ally

ele

ctro

lyti

c ca

pac

ito

rs a

re

pol

ariz

ed . H

owev

er, t

his

one

is b

ipol

ar

mea

nin

g i

t ca

n b

e in

stal

led

in

eit

her

di

rect

ion .

Wra

p o

ne le

ad to

turr

et 2

3 an

d th

e ot

her l

ead

to tu

rret

52 .

Ad

d a

2-1/

2" y

ello

w ju

mp

er to

turr

et 5

2 .

Ad

d a

3" g

reen

jum

per

to tu

rret

23 .

S

TE

P 6

1

Ad

d t

wo

res

isto

rsA

dd

one

68k

resi

stor

bet

wee

n tu

rret

s 22

an

d 34

.

Add

ano

ther

68k

resi

stor

bet

wee

n tu

rret

s 21

and

34 .

S

TE

P 6

2

Ad

d t

hre

e ju

mp

ers

Cut t

wo

2" y

ello

w ju

mp

ers .

Ad

d th

e fir

st ju

mp

er to

turr

et 2

2 .

Ad

d th

e se

cond

jum

per

to tu

rret

21 .

Ad

d a

4-1/

2" y

ello

w ju

mp

er t

o tu

rret

34 .

Ru

n t

his

ju

mp

er s

trai

gh

t d

own

to

th

e b

otto

m o

f th

e tu

rret

boa

rd a

nd b

end

it ov

er t

he e

dge

of t

he b

oard

to

keep

it in

p

lace

.

S

TE

P 6

3

Ad

d fo

ur

resi

sto

rsA

dd

one

68k

resi

stor

bet

wee

n tu

rret

s 19

an

d 26

.

Add

ano

ther

68k

resi

stor

bet

wee

n tu

rret

s 18

and

26 .

Ad

d o

ne 1

00k

resi

stor

bet

wee

n tu

rret

s 33

and

50 .

Ad

d a

no

ther

10

0k

resi

sto

r b

etw

een

turr

ets

33 a

nd 5

1 .

S

TE

P 6

4

Ad

d t

wo

cap

acit

ors

Ad

d a

.022

μF c

apac

itor

bet

wee

n tu

rret

s 20

and

51 .

Thi

s an

d th

e fo

llow

ing

yello

w

cap

acit

ors

are

no

t p

ola

rize

d,

so y

ou

can

inst

all t

hem

in e

ither

dire

ctio

n . W

e re

com

men

d fa

cing

them

all

in th

e sa

me

dir

ecti

on

, m

akin

g t

hei

r p

rin

ted

sp

ecs

easy

to re

ad .

Ad

d an

othe

r .0

22μF

cap

acito

r b

etw

een

turr

ets

17 a

nd 5

0 .

S

TE

P 6

5

Ad

d fo

ur

jum

per

sCu

t tw

o 2"

yel

low

jum

per

s .

Ad

d th

e fir

st ju

mp

er to

turr

et 1

9 .

Ad

d th

e se

cond

jum

per

to tu

rret

18 .

Add

a 5

-1/2

" yel

low

jum

per

to tu

rret

20 .

Ad

d a

6-1/

2" y

ello

w ju

mp

er to

turr

et 1

7 .

S

TE

P 6

6

Ad

d t

wo

mo

re ju

mp

ers

Ad

d a

3-1/

2" y

ello

w ju

mp

er to

turr

et 5

1 .

Ad

d a

2-1/

2" y

ello

w ju

mp

er to

turr

et 5

0 .

S

TE

P 6

7

Ad

d t

wo

res

isto

rs +

on

e ca

pac

ito

rA

dd

a 2

70k

resi

sto

r b

etw

een

tu

rret

s 16

and

25 .

Ad

d a

270

k re

sist

or

bet

wee

n t

urr

ets

15 a

nd 2

5 .

Ad

d a

500

pF

cap

bet

wee

n tu

rret

s 15

an

d 25

.

S

TE

P 6

8

Ad

d t

hre

e ju

mp

ers

Ad

d a

4-1/

2" y

ello

w ju

mp

er to

turr

et 1

6 .

Ad

d a

6" y

ello

w ju

mp

er to

turr

et 1

5 .

Ad

d a

6" y

ello

w ju

mp

er to

turr

et 2

5 .

S

TE

P 6

9

Ad

d t

wo

res

isto

rs w

ith

ext

ensi

on

sCu

t one

1" y

ello

w ju

mp

er a

nd re

mov

e th

e in

sula

tion .

Wra

p a

nd s

old

er t

his

jum

per

ar

ound

one

lead

of

an 8

20Ω

res

isto

r to

ex

tend

the

lead

of t

he re

sist

or . D

oing

this

w

ill a

llow

the

res

isto

r to

rea

ch b

etw

een

turr

ets

14 a

nd 4

9 .

Add

this

820

Ω re

sist

or w

ith th

e ex

tens

ion

bet

wee

n tu

rret

s 14

and

49 .

Cut a

noth

er 1

" yel

low

jum

per

and

rem

ove

the

insu

lati

on

. W

rap

an

d s

old

er t

his

ju

mp

er a

roun

d on

e le

ad o

f a 1

00K

resi

stor

to

ext

end

the

lead

of t

he re

sist

or . A

dd th

is

resi

stor

bet

wee

n tu

rret

s 14

and

48 .

S

TE

P 7

0

Ad

d o

ne

cap

acit

or

+ t

hre

e ju

mp

ers

Ad

d a

25

0p

F Si

lve

r M

ica

cap

acit

or

bet

wee

n tu

rret

s 32

and

48 .

Ad

d a

3" y

ello

w ju

mp

er to

turr

et 4

9 .

Ad

d a

2-1/

2" y

ello

w ju

mp

er to

turr

et 4

8 .

Ad

d an

8"

jum

per

to

turr

et 3

2 . R

un t

his

turr

et u

p t

owar

d t

he

top

of

the

boa

rd

and

ben

d it

over

the

ed

ge o

f th

e b

oard

to

kee

p it

in p

lace

.

Ad

d a

3" g

reen

jum

per

to tu

rret

14 .

stew

mac

.co

m

30

©

2019

Ste

wM

ac

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

.022μF

.022μF

.022μF

.1μF

.1μF

.1μF

47

5W 1K

stew

mac

.co

m

31

©

2019

St

ewM

ac

S

TE

P 7

1

Ad

d o

ne

resi

sto

r +

tw

o c

apac

ito

rsA

dd

a 5

6k r

esis

tor

bet

wee

n t

urre

ts 4

7 an

d 48

.

Ad

d a

.022

uF c

apac

itor

bet

wee

n tu

rret

s 13

and

47 .

Ad

d an

othe

r .0

22uF

cap

acito

r b

etw

een

turr

ets

12 a

nd 4

7 .

S

TE

P 7

2

Ad

d t

wo

jum

per

s A

dd

a 7-

1/2"

yel

low

jum

per

to tu

rret

13 .

Ad

d an

8" y

ello

w ju

mp

er to

turr

et 1

2 .

S

TE

P 7

3

Ad

d o

ne

resi

sto

r +

on

e ju

mp

erCu

t one

1" y

ello

w ju

mp

er a

nd re

mov

e th

e in

sula

tion .

Wra

p a

nd s

old

er t

his

jum

per

ar

ound

one

lead

of a

10K

2W

res

isto

r to

ex

tend

the

lead

of t

he re

sist

or .

Ad

d t

his

10

K 2

W r

esi

sto

r w

ith

th

e ex

tens

ion

bet

wee

n tu

rret

s 11

and

46 .

Ad

d a

2-3/

4" y

ello

w ju

mp

er to

turr

et 4

6 .

S

TE

P 7

4

Ad

d fo

ur

resi

sto

rsA

dd

a 47

0Ω r

esis

tor

bet

wee

n tu

rret

s 31

an

d 44

.

Ad

d a

1M

res

isto

r b

etw

een

tu

rret

s 31

an

d 45

.

Ad

d an

othe

r 1M

resi

stor

bet

wee

n tu

rret

s 31

and

43 .

Ad

d a

10K

res

isto

r b

etw

een

tu

rret

s 9

and

31 .

S

TE

P 7

5

Inst

all t

wo

cap

acit

ors

+ fo

ur

jum

per

sA

dd

a .

022μ

F ca

p b

etw

een

tu

rret

s 10

an

d 45

.

Ad

d a

.1μF

cap

bet

wee

n tu

rret

s 9

and

43 .

Ad

d a

5" y

ello

w ju

mp

er to

turr

et 1

0 .

Ad

d a

4" y

ello

w ju

mp

er to

turr

et 4

5 .

Ad

d a

2" y

ello

w ju

mp

er to

turr

et 4

4 .

Ad

d a

1-1/

2" y

ello

w ju

mp

er to

turr

et 4

3 .

S

TE

P 7

6

Ad

d fo

ur

resi

sto

rsA

dd

a 10

0K r

esis

tor

bet

wee

n tu

rret

s 30

an

d 42

.

Ad

d an

82K

res

isto

r b

etw

een

turr

ets

30

and

41 .

Ad

d a

220

K re

sist

or b

etw

een

turr

ets

8 an

d 24

.

Ad

d a

no

ther

220

K r

esis

tor

bet

wee

n tu

rret

s 7

and

24 .

S

TE

P 7

7

Ad

d t

hre

e ca

pac

ito

rs a

nd

tw

o

jum

per

sA

dd

a 47

pF

cap

bet

wee

n tu

rret

s 41

and

42

.

Ad

d a

.1μF

cap

bet

wee

n tu

rret

s 8

and

42 .

Ad

d a

not

her

.1μ

F ca

p b

etw

een

turr

ets

7 an

d 41

.

Ad

d a

2" y

ello

w ju

mp

er to

turr

et 4

2 .

Ad

d a

3-3/

4" y

ello

w ju

mp

er to

turr

et 4

1 .

S

TE

P 7

8

Ad

d o

ne

res

isto

r +

tw

o ju

mp

ers

Cut t

wo

1" y

ello

w ju

mp

er a

nd re

mov

e th

e in

sula

tion .

Wra

p a

nd s

old

er o

ne ju

mp

er

aro

un

d o

ne

lead

of

a 27

K r

esis

tor

to

exte

nd th

e le

ad o

f the

resi

stor

.

Ad

d t

his

27K

res

isto

r w

ith

ext

ensi

on

bet

wee

n tu

rret

s 6

and

40 .

Ad

d a

7" y

ello

w ju

mp

er to

turr

et 6

.

Ad

d a

4" y

ello

w ju

mp

er to

turr

et 4

0 .

S

TE

P 7

9

Ad

d t

wo

res

isto

rs +

on

e ju

mp

erA

dd

a 1

0K 2

W r

esis

tor

bet

wee

n tu

rret

s 5

and

29 .

Ad

d a

1K 5

W re

sist

or b

etw

een

turr

ets

29

and

39 .

Ad

d a

2-1/

2" y

ello

w ju

mp

er to

turr

et 3

9 .

S

TE

P 8

0

Ad

d t

hre

e ju

mp

ers

Cut

a 3-

1/2"

gre

en ju

mp

er a

nd r

emov

e th

e in

sula

tion .

Sta

rtin

g at

tur

ret

2, w

rap

in

a f

igu

re 8

pat

tern

aro

un

d t

urr

et 3

, co

mp

lete

ly a

roun

d tu

rret

4, a

nd t

hen

in

an o

ppos

ite fi

gure

8 p

atte

rn a

roun

d tu

rret

3,

and

bac

k to

turr

et 2

. Thi

s cr

eate

s a

bus

co

nnec

ting

turr

ets

2, 3

, and

4 .

Cu

t tw

o 1

" g

reen

ju

mp

er a

nd

rem

ove

thei

r ins

ulat

ion .

Wra

p o

ne a

roun

d tu

rret

s 37

an

d 3

8 an

d w

rap

th

e ot

her

aro

und

turr

ets

35 a

nd 3

6 .

stew

mac

.co

m

32

©

2019

Ste

wM

ac

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

+ 8µF

+ 8µF

stew

mac

.co

m

33

©

2019

St

ewM

ac

S

TE

P 8

1

Ad

d o

ne

resi

sto

r +

tw

o c

apac

ito

rsA

dd

a 6

8K r

esis

tor

bet

wee

n t

urr

ets

4 an

d 28

.

Ad

d a

n 8

μF

ele

ctro

lyti

c ca

pac

ito

r b

etw

een

tu

rret

s 3

and

37 .

Th

is c

ap i

s p

olar

ized

, so

be

sure

the

neg

ativ

e le

ad

goes

to

turr

et 3

7 an

d th

e p

ositi

ve le

ad

to tu

rret

3 .

Ad

d a

noth

er 8

μF

elec

trol

ytic

cap

acito

r b

etw

een

turr

ets 2

and

36 .

Thi

s cap

is a

lso

pol

ariz

ed, s

o b

e su

re t

he n

egat

ive

lead

go

es t

o tu

rret

36

and

the

pos

itive

lead

to

turr

et 2

.

S

TE

P 8

2

Ad

d o

ne

jum

per

Ad

d a

3" g

reen

jum

per

to tu

rret

2 . R

oute

th

is ju

mp

er to

the

left

of t

he tu

rret

boa

rd .

S

TE

P 8

3

Ad

d t

wo

res

isto

rs a

nd

a d

iod

eA

dd

a 2

20K

resi

stor

bet

wee

n tu

rret

s 1

and

27 .

Ad

d a

15K

res

isto

r b

etw

een

tur

rets

36

and

37 .

Ad

d th

e 1N

4007

dio

de

bet

wee

n tu

rret

s 27

and

35 .

No

te t

he

po

lari

ty o

f th

e d

iod

e . T

he

pos

itiv

e le

ad o

f th

e d

iod

e is

in

dic

ated

by

a s

trip

e at

tha

t en

d . T

he e

nd w

ith n

o st

ripe

is n

egat

ive .

Con

nect

the

nega

tive

lead

to

turr

et 3

5 . C

onne

ct t

he p

osit

ive

lead

to tu

rret

27 .

Sto

p a

nd

insp

ect

you

r w

ork

All

the

com

pon

ents

and

wire

s are

now

on

the

turr

et b

oard

. Tak

e a

bre

ak to

rest

you

r ey

es b

efor

e m

akin

g su

re y

ou’v

e fo

llow

ed

each

ste

p c

orre

ctly

.

To fi

nd n

o m

ista

kes

at t

his

stag

e w

ould

b

e su

rpris

ing,

and

it’s

muc

h le

ss w

ork

to

find

them

now

tha

n af

ter

sold

erin

g! A

s yo

u ch

eck

your

wor

k, m

ake

sure

all

the

conn

ectio

ns a

re ti

ght .

S

TE

P 8

4

Sold

er t

he

com

po

nen

ts o

n t

he

turr

et b

oar

dIt

’s t

ime

to s

et a

ll th

e co

nnec

tions

with

so

lder

.

Revi

ew t

he

tip

s fo

r g

reat

sol

der

ing

on

pag

e 9,

the

n so

lder

eac

h co

nnec

tion

on

the

turr

et b

oard

.

Aft

er a

ll th

e jo

ints

are

sol

der

ed c

lip t

he

exce

ss le

ads

from

the

tur

rets

. Trim

min

g th

e ex

cess

lead

s is

imp

orta

nt t

o av

oid

a sh

ort i

n yo

ur c

ircui

t . C

heck

all

your

sold

er

join

ts t

o m

ake

sure

the

y’re

shi

ny, a

nd t

o se

e th

at y

ou d

idn’

t mis

s on

e .

STOP

Be fus

sy Fin

d the

mistak

e now

, not

later!

Sold

er c

om

po

nen

ts t

o t

urr

et b

oar

d

stew

mac

.co

m

34

©

2019

Ste

wM

ac

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

Beh

ind

bo

ard

vie

w

stew

mac

.co

m

35

©

2019

St

ewM

ac

S

TE

P 8

5

Ad

d t

en b

ehin

d-t

he-

bo

ard

jum

per

sTh

e w

iring

dia

gram

ab

ove

is n

ow a

vie

w

of t

he t

urre

t b

oard

flip

ped

ove

r . O

rient

yo

ur b

oard

as

show

n in

the

dia

gram

to

sim

plif

y in

stal

lati

on

of

the

beh

ind

th

e b

oard

jum

per

s .

Cu

t th

ese

jum

per

s to

len

gth

an

d t

rim

3/

8" o

f sh

ield

ing

off e

ach

end

. Run

the

ex

pos

ed e

nds

up in

to th

e b

otto

m o

f the

tu

rret

s an

d so

lder

them

into

pla

ce .

Cut

a 4"

yel

low

jum

per

and

sol

der

one

en

d t

o th

e b

otto

m o

f tu

rret

26 .

Rou

te

the

free

end

str

aigh

t d

own

tow

ard

the

b

otto

m o

f th

e b

oar

d, b

etw

een

tur

rets

50

and

51 .

Cut a

noth

er 4

" yel

low

jum

per

and

sol

der

on

e en

d to

the

bot

tom

of t

urre

t 33 .

Pla

ce

the

othe

r end

in th

e b

otto

m o

f tur

ret 4

6 b

ut d

on't

sold

er it

yet

.

Cut

a 12

" ye

llow

jum

per

and

sol

der

one

en

d to

the

bot

tom

of t

urre

t 46

with

the

ju

mp

er a

lread

y in

pla

ce . R

oute

the

fre

e en

d of

this

jum

per

tow

ard

turr

et 2

7 .

Cut

a 3"

yel

low

jum

per

and

sol

der

it t

o th

e b

ack

of

turr

et 3

0 . P

lace

th

e o

ther

en

d in

to th

e b

otto

m o

f tur

ret 5

but

don

’t so

lder

it y

et .

Cut a

n 8-

1/2"

yel

low

jum

per

and

ad

d on

e en

d to

the

bot

tom

of

turr

et 5

but

don

't so

lder

this

yet

eith

er . R

oute

the

free

end

of

this

jum

per

tow

ard

turr

et 2

7 .

Cut

a 4"

yel

low

jum

per

and

sol

der

one

en

d t

o th

e b

otto

m o

f tu

rret

5 w

ith t

he

oth

er t

wo

ju

mp

ers

alre

ady

in p

lace

. So

lder

the

othe

r end

of t

his

4" ju

mp

er to

th

e b

otto

m o

f tur

ret 1

1 .

Sold

er o

ne e

nd o

f a 2

-1/4

" yel

low

jum

per

to

the

bot

tom

of t

urre

t 6

and

sold

er t

he

othe

r end

to th

e b

otto

m o

f tur

ret 9

.

Cut

an 8

" ye

llow

jum

per

and

sol

der

one

en

d to

the

bot

tom

of t

urre

t 29 .

Rou

te th

e fr

ee e

nd to

war

d tu

rret

27 .

Cut a

4-1

/2" y

ello

w ju

mp

er a

nd so

lder

one

en

d to

the

bot

tom

of t

urre

t 28 .

Rou

te th

e fr

ee e

nd to

war

d tu

rret

27 .

Cut a

5-3

/4" y

ello

w ju

mp

er a

nd so

lder

one

en

d to

the

bot

tom

of t

urre

t 24 .

Rou

te th

e fr

ee e

nd to

war

d tu

rret

27 .

Cut

a 4"

yel

low

jum

per

and

sol

der

one

en

d to

the

bot

tom

of t

urre

t 38 .

Rou

te th

e fr

ee e

nd to

war

d tu

rret

27 .

S

TE

P 8

6

Ad

d t

wo

mo

re b

ehin

d-t

he-

bo

ard

ju

mp

ers

Cut

a 5"

yel

low

jum

per

and

a 6

" ye

llow

ju

mp

er . S

trip

1"

of in

sula

tion

fro

m o

ne

end

of e

ach .

Ad

d a

5 .1K

resi

stor

to th

e st

ripp

ed e

nd o

f ea

ch o

f th

ese

jum

per

s . O

nce

the

sold

er

join

ts c

oo

l, ad

d 1

" o

f 1/

8" h

eat-

shri

nk

tub

ing

to in

sula

te th

e so

lder

join

t .

On

ce t

he

hea

t sh

rink

co

ols,

sol

der

th

e re

sist

or fr

ee e

nd o

f the

5"

jum

per

to

the

bot

tom

of t

urre

t 8 . R

oute

the

end

of th

is

jum

per

with

the

resi

stor

att

ache

d to

war

d tu

rret

37 .

Sold

er t

he

resi

sto

r fr

ee e

nd

of

the

6"

jum

per

to

the

bot

tom

of t

urre

t 7 .

Rou

te

the

end

of t

his

jum

per

with

the

res

isto

r at

tach

ed to

war

d tu

rret

27 .

S

TE

P 8

7

Ch

eck

the

con

tin

uit

y o

f yo

ur

bac

k-o

f-b

oar

d ju

mp

ers

On

ce a

ll o

f th

ese

sold

er

join

ts a

re

set,

flip

th

e b

oar

d b

ack

over

an

d t

est

for

con

tin

uit

y o

n e

ach

pai

r o

f tu

rret

s co

nnec

ted

by

bac

k-of

-boa

rd r

uns .

Use

a

mul

tim

eter

for

con

tinu

ity

test

ing

, as

des

crib

ed o

n p

age

43 .

You

sh

ou

ld h

ave

con

tin

uit

y o

n t

he

follo

win

g p

airs

of t

urre

ts:

n

tur

ret 3

3 to

turr

et 4

6

n

tur

ret 5

to tu

rret

11

n t

urre

t 30

to tu

rret

5

n t

urre

t 6 to

turr

et 9

S

TE

P 8

8

Org

aniz

e th

e b

ehin

d-t

he-

bo

ard

ju

mp

ers

Twis

ting

som

e of

thes

e ju

mp

ers t

oget

her

wil

l h

elp

org

aniz

e t

he

m f

or

eas

ier

asse

mb

ly la

ter,

and

it w

ill h

elp

kee

p th

em

tid

y in

th

e lo

ng

run

. Rem

emb

er, g

oo

d le

ad d

ress

mea

ns le

ss n

oise

. (se

e p

age

37)

Thre

e of

the

se ju

mp

ers

will

be

goin

g to

th

e fil

ter c

apac

itors

mou

nted

aga

inst

the

sid

e w

all .

Thes

e ju

mp

ers

will

be

carr

ying

hi

gh v

olta

ge t

o th

e tu

rret

boa

rd, s

o w

e w

ant t

o tw

ist t

hem

toge

ther

to k

eep

them

ne

at a

nd a

way

from

sign

al c

arry

ing

wire

s .

Twis

t the

jum

per

s co

min

g fr

om tu

rret

s 5,

29

, and

46

toge

ther

. Kee

p t

hem

rou

ted

pas

t tur

ret 2

7 on

ce th

ey a

re t

wis

ted

.

Twis

ting

the

jum

per

s to

the

bia

s p

ot is

al

so a

goo

d id

ea . T

hese

jum

per

s co

me

from

tur

rets

24,

28,

and

38 .

Tw

ist

them

to

get

her

an

d r

ou

te t

he

twis

ted

lea

ds

pas

t tur

ret 2

7 .

Mak

e su

re t

he ju

mp

er f

rom

the

bac

k of

tu

rret

8 is

rout

ed p

ast t

urre

t 37,

and

mak

e su

re t

he ju

mp

er f

rom

tur

ret

7 is

rou

ted

pas

t tur

ret 2

7 .

S

TE

P 8

9

Glu

e b

ehin

d-t

he-

bo

ard

jum

per

s d

ow

nA

s yo

ur

amp

ag

es,

it w

ill n

eed

par

ts

rep

lace

d .

Wh

en y

ou

hea

t a

turr

et t

o re

mov

e a

wor

n-o

ut p

art,

a b

ehin

d-t

he-

bo

ard

ju

mp

er c

ou

ld c

om

e d

islo

dg

ed

from

the

bac

k of

the

tur

ret,

intr

oduc

ing

a w

hole

new

pro

ble

m . T

o p

reve

nt t

his,

ap

ply

a d

ime

size

d a

mou

nt o

f co

ntac

t ce

men

t to

eac

h w

ire'

s in

sula

tio

n a

s sh

own .

Thi

s w

ill h

old

the

jum

per

s tig

ht

to th

e b

ack

of th

e b

oard

eve

n w

hen

you

heat

the

turr

et a

nd s

old

er li

quefi

es .

Allo

w t

his

glue

to c

ure

over

nigh

t . Th

is is

a

good

cha

nce

to s

top

and

dou

ble

che

ck

all

of y

our

conn

ecti

ons

one

mor

e ti

me

bef

ore

inst

allin

g t

he t

urre

t b

oard

in t

o th

e ch

assi

s .

stew

mac

.co

m

36

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

12

43

12

43

AA BB

12

43

12

43

AA BB

1MA

1MA

25KL

250KL

5KL

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

250

stew

mac

.co

m

37

©

2019

St

ewM

ac

You

're

read

y to

inst

all t

he

turr

et

bo

ard

in t

he

chas

sis.

It’s

tim

e to

rem

ove

yo

ur

tap

e w

ith

the

turr

et n

umb

ers .

Wh

en t

he

bo

ard

’s

inst

alle

d, y

ou w

on’t

be

able

to g

et a

t the

ta

pe

to r

emov

e it

. Fro

m t

his

poi

nt o

n,

you

can

iden

tify

jum

per

s an

d tu

rret

s by

re

ferr

ing

to th

e di

agra

ms .

S

TE

P 9

0

Ad

d t

he

last

filt

er c

ho

ke le

adBe

fore

mou

ntin

g th

e tu

rret

boa

rd in

the

chas

sis,

sol

der

the

last

filte

r ch

oke

lead

to

the

bot

tom

of t

urre

t 29

alon

g w

ith th

e ju

mp

er a

lread

y in

pla

ce .

S

TE

P 9

1

Inst

all t

he

turr

et b

oar

dTo

kee

p t

he

turr

et b

oar

d c

on

nec

tio

ns

from

sho

rtin

g ag

ains

t th

e m

etal

cha

ssis

, th

e b

oard

is m

ount

ed o

n fo

ur t

hrea

ded

st

and

off

s th

at h

old

it

away

fro

m t

he

chas

sis

Use

4-4

0 sc

rew

s to

mo

un

t th

ese

fou

r st

ando

ffs t

o th

e ch

assi

s . L

ine

up th

e tu

rret

b

oard

on

thes

e st

and

offs .

S

TE

P 9

2

Sold

er t

he

no

rmal

ch

ann

el ja

cks

Sold

er th

e ju

mp

er fr

om tu

rret

21

to lu

g 4

of n

orm

al c

hann

el ja

ck B

.

Sold

er th

e ju

mp

er fr

om tu

rret

22

to lu

g 4

of n

orm

al c

hann

el ja

ck A

.

Sold

er th

e ju

mp

er fr

om tu

rret

23

to lu

g 2

of n

orm

al c

hann

el ja

ck A

.

S

TE

P 9

3

Sold

er t

he

hig

h t

reb

le c

han

nel

jack

sSo

lder

the

jum

per

from

turr

et 1

9 to

lug

4 of

hig

h tr

eble

cha

nnel

jack

B .

Sold

er th

e ju

mp

er fr

om tu

rret

18

to lu

g 4

of h

igh

treb

le c

hann

el ja

ck A

.

S

TE

P 9

4

Sold

er t

he

no

rmal

ch

ann

el lo

ud

nes

s p

ot

Sold

er t

he ju

mp

er f

rom

tur

ret

20 t

o th

e rig

ht lu

g of

the

norm

al c

hann

el lo

udne

ss

pot

.

Sold

er t

he

jum

per

fro

m t

urr

et 1

6 to

th

e m

idd

le l

ug

of

the

no

rmal

ch

ann

el

loud

ness

pot

.

Sold

er t

he ju

mp

er f

rom

tur

ret

14 t

o th

e b

ack

of th

e no

rmal

cha

nnel

loud

ness

pot

.

S

TE

P 9

5

Sold

er t

he

hig

h t

reb

le c

han

nel

lo

ud

nes

s p

ot

Ad

d a

250

pF

cap

acit

or

bet

wee

n t

he

right

and

mid

dle

lugs

of t

he h

igh

treb

le

chan

nel

loud

ness

pot

but

don

't so

lder

th

e le

ads

yet .

Sold

er t

he

jum

per

fro

m t

urr

et 1

7 to

th

e rig

ht lu

g of

the

hig

h tr

eble

cha

nnel

lo

udn

ess

pot

alo

ng

wit

h th

e ca

pac

itor

le

ad a

lread

y in

pla

ce .

Sold

er t

he ju

mp

er f

rom

tur

ret

15 t

o th

e m

idd

le l

ug

of

the

hig

h t

reb

le c

han

nel

lo

udn

ess

pot

alo

ng

wit

h th

e ca

pac

itor

le

ad a

lread

y in

pla

ce .

S

TE

P 9

6

Sold

er t

he

treb

le p

ot

Sold

er t

he ju

mp

er f

rom

tur

ret

32 t

o th

e rig

ht lu

g of

the

treb

le p

ot .

Sold

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he ju

mp

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rom

tur

ret

10 t

o th

e m

iddl

e lu

g of

the

treb

le p

ot .

Sold

er th

e ju

mp

ers

from

turr

et 1

3 to

the

left

lug

of th

e tr

eble

pot

.

S

TE

P 9

7

Sold

er t

he

mid

s p

ot

Sold

er t

he ju

mp

er f

rom

tur

ret

12 t

o th

e m

iddl

e lu

g of

the

mid

s p

ot .

S

TE

P 9

8

Sold

er t

he

pre

sen

ce p

ot

Sold

er t

he j

ump

er f

rom

tur

ret

6 to

the

rig

ht lu

g of

the

pre

senc

e p

ot .

S

TE

P 9

9

Sold

er t

he

gro

un

d ju

mp

erSo

lder

the

gre

en j

ump

er f

rom

tur

ret

2 to

the

3-lu

g gr

ound

ing

stri

p u

nder

the

p

rese

nce

pot

.

Four

sta

ndo

s

Inst

alli

ng

th

e tu

rret

bo

ard

in t

he

chas

sis

Tip

s fo

r le

ad d

ress

wit

h ju

mp

ers

As

gen

eral

ru

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or

inst

alli

ng

th

ese

jum

per

s, w

hen

two

jum

per

s cr

oss

over

ea

ch o

ther

, ben

d th

em s

o th

ey c

ross

at

90°

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es r

athe

r ru

nnin

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de-

by-

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e .

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lead

dre

ss d

etai

l infl

uenc

es th

e am

p’s

soun

d, e

spec

ially

on

a hi

gh-g

ain

circ

uit

like

this

one

.

stew

mac

.co

m

38

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

-

4 3

21

87

65

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

-

D C

-

B A

-

1

23

4

12

43

12

43

12

43

12

43

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

stew

mac

.co

m

39

©

2019

St

ewM

ac

S

TE

P 1

00

Sold

er t

he

jum

per

s to

V1

Sold

er t

he ju

mp

er f

rom

tur

ret

51 t

o V1

p

in 1

.

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er t

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mp

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rom

tur

ret

50 t

o V1

p

in 6

.

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he

beh

ind

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um

per

fr

om tu

rret

26

to V

1 p

in 7

.

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mp

er f

rom

tur

ret

34 t

o V1

p

in 2

.

Sold

er th

e ju

mp

er fr

om tu

rret

52

to V

1 pi

n 8

alon

g w

ith th

e ju

mp

er a

lread

y in

pla

ce .

S

TE

P 1

01

Sold

er t

he

jum

per

s to

V2

Sold

er t

he ju

mp

er f

rom

tur

ret

46 t

o V2

p

in 6

alo

ng w

ith th

e re

sist

or le

ad a

lread

y in

pla

ce .

Sold

er t

he ju

mp

er f

rom

tur

ret

48 t

o V2

p

in 8

.

Sold

er t

he ju

mp

er f

rom

tur

ret

49 t

o V2

p

in 3

.

Sold

er t

he ju

mp

er f

rom

tur

ret

25 t

o V2

p

in 2

.

S

TE

P 1

02

Sold

er t

he

jum

per

s to

V3

Sold

er t

he ju

mp

er f

rom

tur

ret

41 t

o V3

p

in 1

.

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er t

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mp

er f

rom

tur

ret

42 t

o V3

p

in 6

.

Sold

er t

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mp

er f

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tur

ret

43 t

o V3

p

in 7

.

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er t

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mp

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rom

tur

ret

45 t

o V3

p

in 2

.

Sold

er th

e ju

mp

er fr

om tu

rret

44

to V

3 pi

n 8

alon

g w

ith th

e ju

mp

er a

lread

y in

pla

ce .

S

TE

P 1

03

Sold

er t

he

jum

per

s to

V4

Sold

er t

he ju

mp

er f

rom

tur

ret

39 t

o V4

p

in 6

alo

ng w

ith th

e ju

mp

er a

nd re

sist

or

lead

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ady

in p

lace

.

Sold

er th

e ju

mp

er fr

om tu

rret

8 (r

unni

ng

unde

rnea

th th

e b

oard

with

a 5

.1k

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at

tach

ed to

the

end)

to V

4 pi

n 5 .

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sol

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ery

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tu

be

sock

et, a

s p

ictu

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in th

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agra

m .

S

TE

P 1

04

Sold

er t

he

jum

per

s to

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er th

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om tu

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unni

ng

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th th

e b

oard

with

a 5

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stor

at

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ed to

the

end)

to V

5 pi

n 5 .

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wan

t to

sol

der

thi

s re

sist

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ery

clos

e to

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tu

be

sock

et, a

s p

ictu

red

in th

e di

agra

m .

S

TE

P 1

05

Sold

er t

he

jum

per

s to

V6

Sold

er t

he ju

mp

er f

rom

pin

6 o

f so

cket

V6

to tu

rret

1 .

S

TE

P 1

06

Sold

er o

ne

jum

per

Sold

er th

e ju

mp

er fr

om tu

rret

40

to lu

g 1

of t

he im

ped

ance

sel

ecto

r sw

itch

alon

g w

ith th

e or

ange

out

put

tran

sfor

mer

lead

.

S

TE

P 1

07

Sold

er t

he

jum

per

s to

th

e b

ias

po

tTh

e sh

orte

r set

of t

hree

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ted

jum

per

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to

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th

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per

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ill h

ave

con

tin

uit

y to

tu

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s 24

, 28,

and

38 .

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with

con

tinui

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turr

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28 a

nd s

old

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to th

e le

ft lu

g of

the

bia

s p

ot .

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the

jum

per

with

con

tinui

ty to

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et

24 a

nd s

old

er it

to th

e m

iddl

e lu

g of

the

bia

s p

ot .

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the

jum

per

with

con

tinui

ty to

turr

et

38 a

nd s

old

er it

to

the

righ

t lu

g of

the

b

ias

pot

.

S

TE

P 1

08

Sold

er t

he

jum

per

s to

th

e fi

lter

cap

sTh

e ot

her

set

of t

hree

tw

iste

d ju

mp

ers

com

ing

from

the

lef

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of t

he t

urre

t b

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are

goi

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the

filte

r cap

s . T

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th

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per

s w

ill h

ave

con

tin

uit

y to

tu

rret

s 5,

29,

and

46 .

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the

jum

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with

con

tinui

ty to

turr

et

5 an

d so

lder

it to

filte

r cap

lug

A .

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the

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with

con

tinui

ty to

turr

et

46 a

nd s

old

er it

to fi

lter c

ap lu

g B .

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the

jum

per

with

con

tinui

ty to

turr

et

29 a

nd s

old

er it

to fi

lter c

ap lu

g C

.

stew

mac

.co

m

40

©

2019

Ste

wM

ac

V5 EL34

V4 EL34

POW

ERST

AN

DBY

IND

ICAT

OR

LIG

HT

PRES

ENCE

BASS

MID

DLE

TREB

LEH

IGH

TRE

BLE

LOU

DN

ESS

1N

ORM

AL

LOU

DN

ESS

2IN

PUT

1(H

IGH

TRE

BLE)

INPU

T 2

(NO

RMA

L)

POW

ER IN

LET

FUSE

H.T

. FU

SEIM

PED

AN

CE

V6 5AR4

V3

12A

X7V

212

AX7

V112

AX7

SPEA

KER

EXTE

NSI

ON

SPEA

KER

-

4 3

21

87

65

1 2

1 2

3 41

23

4

12

43

12

43

12

43

12

43

4 3

21

87

65

4 3

21

87

65

6

4 321

98

75

6

4 321

98

75

6

4 321

98

75

2

123 52

5150

4948

4746

4544

4342

4140

3938

37

2824

26

3033

27 35

2931

3225

34

36

34

56

78

910

1112

1314

1516

1718

1920

2122

stew

mac

.co

m

41

©

2019

St

ewM

ac

S

TE

P 1

09

Inst

all t

he

spea

ker

jack

sIn

stal

l th

e la

st c

om

po

nen

t in

to

th

e ch

assi

s, th

e ex

tens

ion

spea

ker j

ack .

The

two

-lug

jack

is th

e ex

tens

ion

spea

ker

jack

and

goe

s to

the

rig

ht o

f th

e m

ain

spea

ker j

ack .

S

TE

P 1

10

Wir

e u

p t

he

spea

ker

jack

sC

ut

a 2"

yel

low

ju

mp

er a

nd

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of t

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en

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to lu

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old

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jum

per

to

lug

1 of

the

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jum

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sold

er it

to

lug

2 of

the

tw

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wra

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to

pin

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3" g

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to lu

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of th

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evie

w y

ou

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ork

Now

you

’ve

sold

ered

th

e co

mp

onen

ts

and

wire

s, a

nd it

's t

ime

to t

ake

a b

reak

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st y

our e

yes a

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view

you

r wor

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care

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sea

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ny e

rror

s b

efor

e yo

u m

ove

on .

STOP


STEP 111

Glue the tube placement chartCut out the chart on page 53 . With a thin coat of glue or contact cement, glue it to the inside wall of the cabinet .

STEP 112

Install the fusesInstall the 3-amp fuse in the mains fuse socket and the 500mA fuse in the H .T . fuse socket .

Installing parts and preparing for testing

STOP!

DON’T INSTALL THE TUBES YET! DON’T PLUG THE AMP IN YET!

The next page is going to keep you out of trouble!

STEP 114

Set the chassis on chassis stand or on blocks for testingSet your chassis up for final testing . Chassis stands are extremely useful for this . If you do not have a chassis stand a couple of blocks of wood can work just fine .

STEP 113

Install the seven control knobsTurn the shaft of each pot all the way counterclockwise to the “off” point and install the knob so the indicator line points to zero . Don't forget the knob for the impedance selector switch on the back .


At this point, dangerous voltage is forming in the filter caps. Always discharge them before working on the circuit, even if the amp is unplugged. See how to use a snuffer stick on page 6 .

For safety, use only one hand to probe the amp during DC tests.

Keep your other hand behind your back when you need to probe a component . This way, you can’t be a path between B+ voltage and ground—a mistake that would send a dangerous charge through your heart .

Set your multimeter to 600V DC and connect the negative lead to ground . Once the negative lead is secured to ground, flip the standby switch to ON . Measure the DC voltage at lug A of the first filter cap . It should be roughly 500V DC .

Turn the power and standby switches to OFF and unplug the amp .

Any multimeter will work fine for the two types of tests we’re about to do: checking continuity and reading voltages . The instructions that came with your meter will be helpful .

Continuity testing is simply making sure current flows between two points successfully . Touch the meter's red lead to one end of the section being tested, and the black lead to the other end . If the continuity is good, your meter will beep or register this on the display .

Voltage testing is where you need to be careful . Some steps require the amp to be plugged in and turned on . This becomes dangerous if you’re not cautious . Respect the voltages and follow the directions, and these tests are safe and easy .

STEP 115

Perform a safe power-upAt this point, there should be no tubes installed, and the speaker should be disconnected .

Before plugging the amp in, turn the power switch to ON . Switching the amp on before the first power-up protects you from shock if a mistake in your wiring has created a short to the chassis . If this short exists, an indication would be that the pilot light will not turn on, since the AC current is going directly to ground .

Plug the power cord in . The pilot lamp should light .

For a few minutes, check for smoke or unusual smells . If anything seems unusual, disconnect the power immediately and carefully review all your connections .

STEP 116

Test the standard AC voltageSet your multimeter to 20V AC . Check the heater voltage across pin 9 and pins 4+5 on the V1 12AX7 socket . This should read between 5-7V AC . If this reading is drastically different, disconnect power and check your connections .

If the amp seems normal, unplug the power cord while still leaving the power switch ON .

Testing and troubleshooting

6

43 2 1

9875

V1

B

A

-

ALWAYS discharge the filter cap

before working on the circuit. See how

to use a snuffer stick on page 6.

And seriously, keep one hand behind

your back!

STEP 117

Test the dangerous DC voltageThe dangerously high DC voltage that passes through the rectifier tube and the filter caps is referred to as “B+” . The next step is to test this B+ voltage .

With the amp still unplugged, install the 5AR4 rectifier tube while spreading the tension clip with the other hand . Take care to position the indexing key correctly in the socket .

Plug the power cord back in . The pilot lamp should light, along with the filament inside the 5AR4 rectifier tube .

Again, spend a few moments checking for smoke or smells .


STEP 118

Test the preamp tubesUnplug the amp use the snuffer stick to discharge the capacitors, then install the three preamp tubes .

After these tubes are installed, plug the amp back in and flip the power switch ON . The pilot lamp should light up . Let the amp warm up for a few minutes and then flip the standby switch to ON . Again, if you get smoke or smells, unplug immediately .

Connect your multimeter’s negative lead to ground .

Set the multimeter to 5V DC and check turret 52, which should read around 1 .3V .

Set the multimeter to 200V DC and check turret 50 . It should read around 200V .

Set the multimeter to 100V DC and test pin 5 of the V7 and V8 sockets . These readings should be nearly identical .

Use a small flathead screwdriver to turn the center of the bias pot all the way counter-clockwise . This will set the bias for the lowest negative DC voltage . Doing this provides a safe voltage for the power tubes while you set the initial bias .

If all of these voltages come within approximately 10% of their expected values, turn the power switch OFF .

Always turn the power switch off before turning the standby switch off . This will drain the filter capacitors as the amp cools down . After a moment, flip the standby switch OFF as well .

If the reading at turret 50 shows no voltage or low voltage, follow this test: unplug the amp, drain the filter caps with the snuffer stick, set your meter to read continuity, and make sure you have properly installed the back-of-board jumper from turret 46 to turret 33 .

STEP 119

Test the EL34 power tubesWith the amp unplugged, install the EL34 power tubes, turning them so their indexing keys fit correctly in the socket . Turn all of the front panel controls completely counter-clockwise, so the indicator line is pointing to "0" .

Connect the amp to a speaker cabinet, adjust the impedance selector switch for the appropriate impedance, and perform these next tests with the speaker turned away from you . If the amp starts to oscillate and squeal, this will help protect your ears .

Plug the amp in and flip the power switch ON . Give the tubes 30 seconds to warm up and then flip the standby switch to ON as well .

After a few moments you should hear a low hum . If the hum becomes very loud, disconnect the power immediately and review your connections .

Set your multimeter to read 500V DC and test for voltage from pin 3 of both socket V5 and socket V4 . This voltage should read around 450V . Write this number in Box 2 of the calculation in Step 121 . It’ll be needed if you use a bias meter to set your bias .

Set your multimeter to read 50V DC and test for voltage at turret 24 . Adjust the bias pot until this voltage reads around -42V .

If all of these voltages come within approximately 10% of their expected values, turn the power switch OFF . After a few moments turn the standby switch OFF as well, and unplug the amp .

Tube bias affects your sound“Bias” refers to the current of electrons flowing from the cathode to the plate inside your power tubes when the tubes are idle . The bias setting determines this flow and is increased or decreased by the screwdriver-adjustable bias pot .

Adjusting the bias affects your sound: a higher setting gives you punchier cleans and grittier distortion, but your tubes will wear out faster . With a low setting, your tubes last longer but the sound is more sterile . A good bias setting falls between these extremes .

STEP 120

Old method of setting the bias: doing it by earIf you have a bias meter, skip this step and go on to Step 121 .

The old-school way of adjusting the bias is by ear: after setting the bias voltage to a recommended starting point, you make tiny adjustments to the bias pot while listening for the sound you want . This inexact method can shorten the life of your power tubes .

You roughed-in the bias setting in the previous step by setting the bias voltage at -42V .

Danger: set your guitar aside before you adjust the bias pot.

Do not touch any amp circuitry while holding your guitar . Doing so would create an electrocution hazard!

Use a screwdriver to make a tiny adjustment to the bias pot . Turn clockwise to increase the current and counter-clockwise to decrease it . Then set the screwdriver aside and play to hear to the result .

Testing and troubleshooting


With the amp unplugged allow the power tubes to cool . Once the power tubes have cooled, remove them from their sockets .

Plug the tubes in to the bias probe sockets, which are like tube sockets . Plug the probe sockets with tubes into the power tube sockets .

Plug the amp back in and flip the power switch ON . Give the tubes 30-60 seconds to warm up, then flip the standby switch ON .

Watch the bias meter as the power tubes heat up . Both needles should rise at an equal rate and settle at the same time .

Adjust your bias pot until the bias meter displays the reading you calculated (33mA in our example) . Let the amp idle for a few minutes to make sure that the bias doesn’t drift .

When you see a constant readout of your bias setting, turn the power switch OFF .

After a few moments flip the standby switch OFF and unplug the amp from the wall .

Once the tubes are cool, remove them and the bias probes from the amp and plug the tubes back into the amp's tube sockets without the probes attached .

After removing the bias probes and taking it for a test drive, if the amp is stable and your tests match the voltages specified, feel free to let it rip!

After playing for a few minutes and testing all inputs, if everything seems to be operating normally, go ahead and turn the amp off .

If there are any strange oscillations, squeals, or the amp seems at all unstable, use a wooden chopstick to begin probing for loose connections: n from the input jacks to the turret boardn from the tube sockets to the turret boardn from the tube sockets to the front panel controls .

It usually takes just a minor wiring adjustment, perhaps resoldering a loose joint, to correct this sort of distortion .

Watch out for red-platingYou especially want to avoid too much current turning the gray plates to glowing red . If your tubes start red plating, shut the amp down and let it cool before setting the bias to a lower level .

STEP 121

Improved method of setting the bias: using a bias meterThe more accurate way to set the bias is by using a bias meter, such as the VHT Bias Tester (StewMac #1580) .

This method starts with a simple calculation to find your bias setting, then you adjust the bias pot until your bias meter displays that reading .

The calculation uses two numbers, the tube’s maximum plate dissipation and its plate voltage .

Plate dissipation . Every power tube has a specified plate dissipation—the maximum wattage the tube can handle . For the EL34 power tubes in this amp, that maximum is 25 watts . Exceeding the 25-watt limit will damage the tube, and operating at the full 25 watts will shorten its life . Our goal is to operate the tube at 60% of the 25-watt limit, or 15 watts . We've entered this number for you in Box 1 of the calculation .

Plate voltage . You already have the plate voltage for these tubes: it’s the the number you found in step 119 and wrote in Box 2 below .

Divide Box 1 by Box 2 . The result is your recommended bias setting for use in the next step . Our example calculation gives a bias recommendation of .034 Amps . Since bias is typically measured in milliamps, this measurement is written as 34mA .

Example:

Your plate voltage from Step 16560% of max. plate dissapation

÷Your bias current setting

=15

BOX 2BOX 1

15 ÷ =


STEP 123

Install the chassisDischarge the capacitors so you can safely handle the chassis . Remove all the cables from their jacks .

Slide the chassis in from the back until its front edge meets the front wall of the cabinet . Insert the mounting screws through the f loor of the chassis . Tighten the locknuts .

Install the preamp tube shields and install the back panel .

Final assembly

Tube lifeThe life span of the power tubes is affected by how hard you drive the amp . If you are overdriving the amp for hours every day, expect the power tubes to have a shorter life span .

We encourage you to experiment with different tube brands and find the brand that is most favorable to your ears and your wallet .

For questions and support, StewMac is here to help!For more than fifty years, StewMac has supplied instrument builders and repair shops . Our customer service team really knows how to help if you run into questions .

Call 800-848-2273 from 9AM–6PM Eastern time, Monday–Friday . Email: service@stewmac .com

Thanks for choosing this StewMac kit, and welcome to the world of amp building!

Tips for using this ampThis amp is known for its rich, articulate clean tones and exceptional sustain: creamy, warm, and a little crispy . If you're looking for AC/DC tones, look no further .

This amp is based on the JTM45 circuit, which is nearly identical to the 5F6A Tweed Bassman circuit . The most notable change is the use of a 12AX7 in V1 instead of a 12AY7 . This gives them amp more gain right out of the gate as the 12AY7 only has a gain factor of 44 compared to the 12AX7's gain factor of 100 .

Despite the wealth of gain in the amp, you will find that it is still very quiet . This is largely due to the large filter caps and the use of the filter choke to smooth out the ripple in the high voltage lines .

The treble, middle, bass tone stack allows you to precisely dial in the exact tone you are looking for . I like to play humbuckers through the high treble channel with a traditional 4x12 Marshall cabinet . With this setup, I prefer to keep the treble around 5, the bass and middle controls around 4, the presence around 4, and the volume around 6 . This positions the amp right on the edge of tube saturation, perfect for kicking on a distortion pedal when you want to take a lead and drive the amp into full-on, tube-saturated glory .

If you are playing through smaller speakers you will probably want to dial the treble and bass back a little bit . If you are using single-coil pickups in your guitar you will most likely want to give yourself a little bump on the bass control and dial your treble back even more .

As with most of these classic amps, it's hard to pull a bad tone from this one . That's why we are still building these circuits half a century later .

Matt Clouston, StewMac

It's finally time to let it rip!

GO!GO!


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OutputGain

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Speaker levelLine level Line level

You don’t need to read a schematic to build this kit . But it’s fun to see how the circuit works, and to see the different subcircuits that interact to shape your sound .

Working with the tiny signal from the guitar, the amp creates the power needed to drive the speaker . The signal is affected by the gain, processing, output and power stages as it passes through the circuit .

The gain circuit increases the signal to line level (about 1 volt), by passing it through a 12AX7 preamp tube where electrons flow from a heated cathode to be received by the anode plate . The grid between these receives the tiny voltage from the guitar, whose varying musical signal controls the flow of electrons to the plate .

This amp’s dirt comes from the first gain stage being biased extremely hot: the small-value 820Ω resistor reduces headroom and increases distortion .

The negative feedback loop flattens and extends the amp’s frequency response, reducing distor tion generated in the output stage . This makes the amp’s sound cleaner and more hi-fi . Some players disable this loop completely or add a potentiometer in place of the resistor to create a “grit control .” We don’t recommend this, because it places stress on the output transformer .

The processing stage shapes the tone . This amp has a universal Treble, Middle, Bass tone control . This allows you to shape each section of the three-band equalizer, and being universal means that the tone controls effect both channels .

The Presence control of this amp uses the negative feedback circuit to introduce more high frequency to the signal, this can be heard as more "bite" to the naked ear . But don't be surprised if the sound engineer at your next gig asks you to turn down the presence, it can be extremely abrasive when mic'd up .

The signal is then sent to the phase inverter which uses all of V3 . The phase inverter then sends the signal to the output section .

The power supply stage provides power to the other circuit stages, as well as the tube heaters .

This circuit receives the AC power from your wall and passes it through the power transformer to create higher voltage . The electricity then goes to the rectifier, which converts it to a pulsing DC current .

This then passes through the filter choke and the filter capacitors . The filter capacitors filter out the pulsing to create a smooth current . As each cap smoothes a bit more, the current is also passing through resistors that lower the voltage .

As the signal from the guitar becomes more amplified, the ripple of DC current becomes less evident and the fully filtered current is sent to the most sensitive part of the amplifier, the first pre-amp tube in the Gain stage .

The output stage increases the line level signal to speaker level, which is typically 8 volts or greater .

Two EL34 tubes drive the output transformer . They receive the split signal, 180 degrees out of phase, amplify those signals, and send them to the output transformer to be recombined into one signal .

T h is t r a ns f o r m e r a djus t s th e impedance to 4, 8, or 16 ohms to drive an external speaker . This amp has an adjustable fixed bias, which means you need to check the bias and possibly make adjustments when you change power tubes .

cathode

plate

grid

We’ve color-coded these stages on our schematic, to show how the parts work together . Symbols for components are in the key at the bottom of the frame .

On the wiring diagram we build step-by-step in these pages, the parts are easier to recognize . But studying these color-coded stages will help you understand where each component fits into the creation of your sound .

Learning more: secrets revealed in the schematic


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It’s your amp. Your tone. You built it!

’57 MINI TWEED 5W AMP KITOne-knob titan of tone.A timeless studio darling whose tiny size hides tremendous punch and versatility .

The 5F1 circuit was meant to be a student amp but wasn’t kid stuff for long; rock’s finest guitarists hijacked it for some of the greatest songs ever recorded . Listen to Eric Clapton (“Layla") or Joe Walsh (“Rocky Mountain Way") while you build this amp!

Our simplest kit; the quickest way to get into amp building .

#10730 5 WATTS / 8" SPEAKER / ORIGINAL 5F1 CIRCUIT

’65 P-REVERB 15W AMP KITSparkling bright, perfect for the surf.Plug your single-coils straight in for that signature clean American tone, or go surfing with onboard effects .

The smallest member of the black-panel family to offer reverb and tremolo, this amp made its name as a jangly pop dream machine . Aficionados treasure its early low-end breakup powered by a pair of 6V6 tubes .

Listen to “Surfin’ USA" and the great sounds of the Heartbreakers .

#10734 15 WATTS / 10" SPEAKER / ORIGINAL AA1164 CIRCUIT

’66 D-REVERB 22W AMP KITFamously clean, with enough guts to gig.Perfect for recording as well as performing, the D-Reverb produces stinging clarity that absolutely refuses to get lost in the mix .

One of the most popular designs ever, this amp lives in the happy middle between bright clarity and rich distortion . It excels in the studio and on the stage . While capable of crystal clear tones at good volume, you can push this one into beautifully saturated, play-sensitive distortion .

It’s all here: clarity, distortion, and rectifier tube sag .

#10737 22 WATTS / 12" SPEAKER / ORIGINAL AB763 CIRCUIT

H OU RS : 6

D I F F I C U LTY

H OU RS : 1 2

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H OU RS : 8

D I F F I C U LTY

H OU RS : 16

D I F F I C U LTY

’59 TWEED 15W AMP KITDirty little devil that shaped guitar history.With mysteriously fat saturated tone, this little monster makes it easy to achieve seismic distortion .

This amp’s 5E3 circuit is an enigma: Why do the controls on the channel you’re NOT using make your tone so great? The answer: Who cares? This is one of the greatest tone monsters ever created! Listen to Neil Young’s Rust Never Sleeps while building this kit .

Our most popular amp kit and a great learning experience .

#10731 15 WATTS / 10" SPEAKER / ORIGINAL 5E3 CIRCUIT

StewMac ICON KITS teach you the world of amp building, then turn you loose with amazing hand-built tone machines!


’62 BRIT-PLEX 45W AMP KITThe original British showstopper.This amp started a revolution . It’s been rocking the world for over 50 years, and we still can’t get enough .

Favored by blues and rock players for exceptional sustain and rich creamy tone, the ’62 Brit-Plex is chock-full of harmonic gain, yet it still stays articulate and even a little crispy . Put this head on a classic 4x10 cab and watch out!

While building, listen to Gary Moore’s “Still Got The Blues ."

#10736 45 WATTS / ORIGINAL BRITISH CIRCUIT

’66 BRIT-74X 18W AMP KITLeave your half-stack at home.Born in London, this little blues blaster earns its living every night, gigging in clubs across the USA .

Launched in 1966, this amp quickly became a low-wattage holy grail . This is a stripped-down blues machine: two channels, one tone knob, no master volume . Buckle up and go where this gritty beast takes you! It comes with a footswitch to kick in the onboard tremolo .

Get the plexi tone without blowing the roof off the joint!

#10732 18 WATTS / 12" SPEAKER / ORIGINAL BRITISH CIRCUIT

’81 BRIT-800 50W AMP KITThis hairy monster lives to shred.The defining British circuit that dominated the ’80s .

This 50W giant created your favorite heavy rock and metal albums . Used by Slayer and Pixies, and recorded on early Metallica albums, this circuit produces that screaming guitar tone that your mother despises . With solid-state rectification there’s no sag, and the distortion created by this circuit is way more about treble than mids or bass .

Listen while building: Smashing Pumpkins’ Siamese Dream .

#10735 50 WATTS / ORIGINAL BRITISH CIRCUIT

’64 REVERB UNIT KITReverb you can’t get from a pedal.This is the unit that put the waves in surf music! Looks like an amp, sounds like a beach party .

This tube-driven reverb tank relies on good ol’ physics for a perfect effect . Your guitar signal travels along two large suspended springs to produce the reverb that launched the iconic surf sound . This isn't a pocket-sized digital simulation; this is the real deal!

Listen to Dick Dale’s “Misirlou" while doing this easy build .

#10733 ORIGINAL 6G15 CIRCUIT

H OU RS : 1 2

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D I F F I C U LTY

H OU RS : 16

D I F F I C U LTY

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D I F F I C U LTY

Beginner-tested. Pro quality.StewMac ICON KITS are fun to build, with friendly instructions to guide you and loads of info to add to your knowledge.


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’62 BRIT-PLEX 45WA M P L I F I E R K I T O R I G I N A L B R I T I S H C I R C U I T

StewMac®

I C O N K I T S

DANGER: Unplug the amp before changing tubes.Tube locations from left to right:

5AR4(GZ34)

EL34 EL3412AX7(ECC83)

V6 V5 V4 V1

12AX7(ECC83)

12AX7(ECC83)

V3 V2

’62 BRIT-PLEX 45WA M P L I F I E R K I T O R I G I N A L B R I T I S H C I R C U I T

StewMac®

I C O N K I T S

DANGER: Unplug the amp before changing tubes.Tube locations from left to right:

5AR4(GZ34)

EL34 EL3412AX7(ECC83)

V6 V5 V4 V1

12AX7(ECC83)

12AX7(ECC83)

V3 V2

Cut this label on the dotted line with a razor knife and metal straightedge .Fasten it inside the cabinet using thinned wood glue or contact cement .

The duplicate copy below is included as a backup .

’62 BRIT-PLEX 45W

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