I.R.T. ELECTRONICS PTY LTD26 Hotham Parade, ARTARMON, N.S.W. 2064 AustraliaPhone: (ISO Code 61) (02) 4393744 Fax: (02) 439 7439 Telex: AA122130

AA-289

10x1 AUDIO SWITCHER

802152 21-08-1985

DESIGNED AND MANUFACTUREDIN AUSTRALIA

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AA-289

10x1 AUDIO SWITCHER

INSTRUCTION BOOK

Section Contents Page

1. General Description 3.

2. Technical Data 4.

3. Circuit Description 5.

4. Installation 7.

5. Circuit Diagrams

6. Parts Lists

W A R N I N G

OPERATION OF ELECTRONIC EQUIPMENT INVOLVES THE USE OF VOLTAGESAND CURRENTS WHICH MAY BE DANGEROUS TO HUMAN LIFE. OPERATINGPERSONNEL SHOULD OBSERVE ALL SAFETY REGULATIONS. DO NOT CHANGECOMPONENTS OR MAKE ADJUSTMENTS INSIDE THE EQUIPMENT WITH POWER ONUNLESS PROPER PRECAUTIONS ARE OBSERVED. NOTE THAT UNDER CERTAINCONDITIONS DANGEROUS POTENTIALS MAY EXIST IN SOME CIRCUITS EVENTHOUGH POWER CONTROLS ARE IN THE OFF POSITION.

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GENERAL DESCRIPTION

The AA-289 Audio Switcher is a ten input Audio Switcherdesigned to operate as the AUDIO FOLLOW Switcher for an IRT VideoSwitcher. For Stereo Audio applications two AA-289 Switchers canbe controlled from one Video Switcher by connecting the Tallycontrol lines to each of the two AA-289 Switchers.

The AA-289 Audio Switcher can also be used as a STAND-ALONEAudio Switcher when it is controlled from a VA-291 Control Panel,again for Stereo applications two AA-289 Switchers can becontrolled from one VA-291 Control Panel by connecting thecontrol data lines of the VA-291 to each of the AA-289 Switchers.

Provision is made on the AA-289 and the VA-291 to link pairs ofthe units together and so implement a 20x1 Audio Switcher.

The input circuit of the AA-289 is designed to bridge across abalanced 600 ohm line. The output circuit will drive two 600 ohmbalanced circuit loads, to a maximum level of +20 dBm.

An internal 240 Volt AC powered regulated Power Supply suppliesthe operating voltages for the AA-289 circuitry.

The AA-289 is housed in an IRT one rack unit (44mm high) 483mm(19 inch) rack mounting metal chassis. The Input and Outputcircuit connections are by means of compression screw terminalstrips mounted on the edge of the main printed circuit board,accessible from the rear panel of the unit. Control input signalsare connected via a pair of 25 pin "D" Connectors mounted on therear panel, which are wired in parallel to allow the looping ofthe control signals to an extra AA-289 for Stereo applications.

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TECHNICAL DATA

Inputs:

Outputs:

Harmonic Distortion:

Noise:

Crosstalk:

Control inputs:

Power requirements:

Dimensions:

Accesories available:

Ten 600 ohm balanced circuit, bridging(10 Kohms) input impedance

Two balanced 600 ohms

Switched common Audio circuit for linkingto another AA-289 when a 20x1 Switcher isimplemented

Maximum Output Level: +20 dBm

Frequency Response: +/- 0.25 dB in the range 20Hz to 15KHz.(Referenced to 1KHz)

Less than 0.2% in the range 20Hz to 15KHzat an Audio level of +16dBm.

With input terminated by 600 ohms:-Less than -90dBm. (Bandwidth 20Hz to15KHz)

Between inputs:- Less than 80dB at 15KHz.(Input of measured channel terminated)

One of 10 grounding circuits.(Internal 4.7 Kohms pull-up resistors to+12 volts)

OR4 bit BCD (TTL Levels)

240V AC 7VA

44mm x 480mm x 230mm

VA-291 Control PanelInstruction manual

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CIRCUIT DESCRIPTION

The Audio Input signals are switched by Relays RL1 to RL10 tothe input circuitry of feedback amplifiers composed of (U8.Q11and Q12) and (U9,Q13 and Q14).the input to each amplifier is ACcoupled to eliminate any DC off-set that may be present on theincoming Audio signal. Each amplifier has a gain of two to boostthe signal level so that an overall gain of unity is achievedwhen the output signal is terminated by a 600 ohm load.The output circuitry is DC coupled through sourcing resistors

R43 to R46 to set the output impedance of the amplifier.

A feature of the circuitry is the isolation between each sideof the balanced Audio circuit, achieved by using non-invertingamplifier circuits. This gives equal loading on each side of thebalanced Audio lines, and allows the AA-289 to be used to switcha Stereo pair of Unbalanced Audio Circuits. Since unbalancedAudio circuits normally have an input impedance greater than 10Kohms the gain in the amplifiers is then not required and couldbe changed to unity by removing resistors R34 and R40.

Note the links LK1 and LK2 which (when completed) allow therelay common Audio circuit to be looped via TB2 to another AA-289when a 20x1 switcher system is implemented.

The Control circuit of the AA-289 is arranged so that thecontrol signal can be either a single ground contact to one often inputs OR a 4 bit BCD (TTL level) signal. The one of tengrounding inputs makes the AA-289 directly compatible with theVA-141 Video Switcher TALLY circuit and thus can be used as anAudio Follow Switcher for the Video Switcher. A ground on one ofthe 10 control inputs is inverted by U2 or U3 and the resultinghigh logic level is passed through an OR gate U4 or U5 to switchon the appropriate relay driver transistor (Ql to Q10). Note the10K ohm, luF RC network in the base circuit of each BC107 relaydriver transistor, this interfaces the 5 volt logic to the basecircuit of the transistor and also acts to give a faster TURN-OFFthan TURN-ON switching action to the transistor . This means thatwhen switching between Audio signals the original signal isreleased a few milliseconds before the next signal is switchedthrough to the output.

The BCD input allows the AA-289 to be used as a STAND-ALONEAudio Switcher together with a VA-291 Control Panel. A VA-291control panel is a 10x1 switch panel with its own encoder andtally circuitry, it requires power from the AA-289 switcher andoutputs a 4 bit BCD (TTL level) signal to control the switchingof a AA-289. Provision is made on a VA-291 to deselect acompanion control panel when two panels are used together withtwo AA-289 switchers to implement a 20x1 Audio Switcher. A 4 bitBCD signal applied to the inputs of Ul will be decoded to a oneof 10 signal to be passed through an OR gate U4 or U5 to switchon the appropriate relay driver transistor.

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CIRCUIT DESCRIPTION

When the one of 10 grounding input circuitry is used to controlthe AA-289, pullup resistors RN3 apply a 1111 signal to inputs ofUl the decimal decoder overranging its circuit and no output willbe selected by it. Note this feature is not available in the 4028decoder 1C of some manufacturers care must be taken ifreplacement is ever necessary.

Similarly when the 4 bit BCD signal is used to control the AA-289, pullup resistors RN1 give logic low signals at the outputsof U2 and U3 and no output will be selected from the one of 10control input circuits.

The power supply consists of two bridge rectifier circuits andthree terminal integrated circuit regulators to provide +/- 15volts to operate the audio amplifiers, +12 volts for the relaysand + 5 volts for the logic circuits.

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INSTALLATION

The AA-289 is housed in a 483mm (19 inch) rack mounting chassisone rack unit (44mm) high.

Signal Connections are by means of compression screw terminalstrips, which plug into sockets mounted on the rear of theprinted circuit board and protruding through the rear panel ofthe chassis. The Input and Output connection sets consist ofgroups of three terminals vis. Active+; Active-; Ground. Input 1to the left of the chassis looking at the rear.

Control Signal Connections are made to a pair of 25 pin 'D'sockets on the rear panel.Note: The 25 pin connectors are wired in parallel to allow one

to be used for control signal wiring from the control switcher orcontrol panel and the other to loop control wiring to a secondAA-289 when pairs of switchers are used as a Stereo Switcher.This eliminates the need for wiring different cable sets to thesame plug.

The Connections are:a) For interfacing to a VA-141A Video Swithcher

Pin 1 Input 1 Grounding control signal" 2 " 2" 3 " 3- 4 " 4" 5 " 5" 6 " 6" 7 " 7" 8 " 811 9 " 9" 10 " 1011 17 GROUND

b)For interfacing to a VA400/410 Video Switcher or VA-291 RCP" 21 Bit A BCD Input (TTL level)11 20 " B" 19 " C.. 18 „ D

" 17 GROUND14 +15 volt power for VA-291 Control Panel

Note 1. when connecting two AA-289 and two VA-291 unitstogether to make a 20x1 Audio Switcher complete links LK1 and LK2on the AA-289 circuit board and wire the two switchers audiocommon circuits together by connections to terminal blocks TB-2.

Note 2. when looping the control signals from a VA-291 controlpanel to two AA-289 switchers for Stereo operation, only loop thecontrol and ground wiring, between the AA-289 swithers. DO NOTloop the +15 volt line. The AA-289 switchers source the +15 voltsto operate the VA-291 circuitry, thus only one AA-289 must haveits +15 volt line connected to the VA-291 control panel.

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Replacem

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List

802152 10x1

AU

DIO

SWITCH

ER A

A-289

ISSUE

3P

age

1 o

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! Part No.

802535

PC802231

PC802233

DN25SY

TB25

L2728

20X5 . 5A

7201-P3

FR2840

802154

802155

802156

801333

801426B

SNU/0520/17/4

801335

133GR10131-220/1020

25.610.0353

25.610.0653

Description .

PCB SUB-ASSEMBLY

PCB CONNECTOR "D"

PCB TRANSFORMER MOUNTING

SOCKET 25 PIN D [PCB]

THREADED BLOCK

FUSED APPLIANCE INLET (IEC320)

20x5mm 500mA

PUSHBUTTON LEVER DPDT

TRANSFORMER POWER

FRONT PANEL AA-289

REAR PANEL AA-289

BASE PLATE AA-289

SIDE PANEL 1R/U

MOUNTING BRACKETS

"U" NUTS 6BA

CHASSIS COVER

LED GRN INCL HOUSING

DIP CABLE ASSEMBLY AA-289

PLUG 3 PIN

8112/3

PLUG 6 PIN

8112/6

Qty1•i1o

2pr1211111222921135

Get Ref.

Jl , 2

Jl,2

FlFlSW1

TlLP2

PI, 2

TB2.3

TB1

SUP16868613520432939111•*26702629996161

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RMF255-100R

RMF255-270R

RMF255-470R

RMF255-1K

RMF255-4K7

RMF255-10K

RSM255-100K

RMF255-lMeg

RSM251-10K

109-4K7

CC27P

CC220P

CC470P

CC100N

CC470N

RB4.7/63

RB10/25

RB47/25

RB470/35

TT1/35

TT2.2/35

TT22/16

1N4004

1N4148

BC107

BC177

9050-09-01

NE5534

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 5%

RESISTOR METAL FILM .25W 1%

RESISTOR NETWORK 9x4K7

CAPACITOR CERAMIC 27pF

CAPACITOR CERAMIC 220pF

CAPACITOR CERAMIC 470pF

CAPACITOR CERAMIC lOOnF

CAPACITOR CERAMIC 470nF

CAPACITOR ELECTRO 4.7uF 63V

CAPACITOR ELECTRO lOuF 25V

CAPACITOR ELECTRO 47uF 25V

CAPACITOR ELECTRO 470uF 35V

CAPACITOR TAG TANT luF 35V

CAPACITOR TAG TANT 2.2uF 35V

CAPACITOR TAG TANT 22uF 16V

DIODE POWER 1A

DIODE 75V 100mA

NPN GP AUDIO TRANSFORMER

PNP GP AUDIO TRANSFORMER

TRANSISTER STANDOFF TO-18

HIGH PERFORMANCE OP-AMP

2421128420412228110423221810122142

R35,41

R43,44,45,46

R31.37

R47

RN1

R21-30,32,36,38,42,RN2,RN4

RN3

Rl-20

R33,34,39,40

RN1

014,21

C15,22

C13.20

016,17,23,24,29,35-37

C28

01-10

011,12,18,19

C38,39

C25,26,27

032,34

030,31

C33

Dll-18

Dl-10

Ql-11,13

Q12.14

Ql-14

U8,9

58:

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58:

58:

58:

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49:

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29:

43:

43:

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92:

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81:

81:

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67:

67:

67:

97:

97:

81814381

802535 10/02/89

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I.R.T. ELECTRONICS PTY.LTD.

Replacement Parts List

802535

PCB SOB-ASSEMBLY AA-289

ISSUE 3

Page 2 of 2

! Part No.

78L05

78L12

7815

7915

6073 THM

4028

40494071

W3108T

W3114T

W3116T

V23100W1112A104

Z5. 598. 6353

Z5. 598. 6653

Z5. 598. 7253

H2072Z01

PC802096

Description.

1C REGULATOR 5V . 1A

1C REGULATOR 12V . 1A

1C REGULATOR 15V 1A

1C REGULATOR -15V 1A

HEAT SINK TO-220

1C DECIMAL DECODER

1C HEX INVERTER

1C QUAD 2 I/P OR

1C SOCKET 8 PIN

1C SOCKET 14 PIN

1C SOCKET 16 PIN

RELAY 2C/0 9- 14V

SOCKET 3 PIN

8112/3

SOCKET 6 PIN 8112/6

SOCKET 12 PIN 8112/12

PCB PINS

PCB AA-289.AA-290

Qty1111112323510312101

Get Ref.

U13

U12

U10

Ull

U10

Ul02,3

U4,5,6

U8.9

U4,5,6

01,2,3,81,2

RL1-10

TB2.3

TB1

TB1

SUP!

97:97:

97:97:

81:97:

97:

97:

99:

99:

99:

69:

61:

61:

61:54:

68:

802535 10/02/89

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