TSQSTG004 R1/00

Quick Shutdown Troubleshooting Guide 4G, H, and X line Progressive Scan Projection Televisions

Use the flowchart on page three to narrow a shutdown cause to a single section, then use theinformation below to find the specific cause of shutdown.

Explanation of SectionsEach section gives the test point(s) for theshutdown monitoring circuits and lists thevoltages for normal operation andshutdown. Once isolated to a section,measure each test point with a peak-response meter to determine whichmonitoring circuit is triggering shutdown.

Section one:The +21V and –21V over currentprotection (OCP) circuits monitor thecurrent flow from the power-2 or sub powersupply to the convergence circuit. If thecurrent increases excessively, shutdownoccurs.Test points:+21V OCP Collector of Q759. Normal operation is 0V. Shutdown occurs at ≥ +0.8V.-21V OCP Collector of Q762. Normal operation is 0V. Shutdown occurs at ≥ -0.8V.

Section two:Because the horizontal deflection and thehigh voltage circuits operate separately,the high voltage circuit can still produce anoutput if the deflection circuit fails. Toprevent burning a line into the CRTs, twohorizontal stop circuits trigger theshutdown circuit and blank the picture if aloss of deflection occurs.The +15V over voltage protection (OVP)circuit monitors the +15V line for excessivevoltage.The X-ray protection circuit, consisting ofQ429 and Q430, monitors the output of thehigh voltage section.Test points:H. Stop 1 and H. Stop 2 Anode of D439. Normal operation is 0V. Shutdown activates at ≥ +2.2V.

+15V OVP Anode of D820. Normal operation is 0V. Shutdown occurs at ≥ +2.2VX-ray Protect Anode of D473. Normal operation is 0V. Shutdown occurs at ≥ +2.2V.

Section Three:The +35V over current protection (OCP)circuit monitors the current flow from the+35V line that supplies the vertical outputQ301 and other switching circuits.Test points:+35 OCP Anode of D371. Normal operation is 0V. Shutdown occurs at ≥ +2.2V.

Section Four:The +125V over voltage protection (OVP)circuit monitors the +125V source of thepower 1 or main power supply. Excessivevoltage at this supply source triggersshutdown.The +125V over current protection (OCP)circuit monitors the current flow from the+125V source to the horizontal deflectionand the high voltage sections.The +21V over voltage protection (OVP)circuit monitors the +21V source of thepower-2 or sub power supply. Excessivevoltage at this supply source triggersshutdown.Test points:+125 OVP Anode of D819. Normal operation is 0V. Shutdown occurs at ≥ +2.2V.+125V OCP Anode of D490. Normal operation is 0V. Shutdown occurs at ≥ +2.2V+21V OVP Anode of D891. Normal operation is 0V. Shutdown occurs at ≥ +2.2V

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QA01Microprocessor

Power 1 SupplyRelay Drivers for SR81

Power 2 SupplyRelay Drivers for SR83

2 of 3 © 2000 Toshiba America Consumer Products, Inc.

5V=Relays on0V=Relays off

> 0.7V = Shutdown0V = NormalR845

R847Q845

D846SCR

K G

A

Q429Q430 X-ray

+5V

D454Q452

D438Q432

D817

D818

R4039Q492

D892

R7756Q762

R7750Q759

R371Q370

D473

Peak-Response MeterWhen shutdown occurs, the relay drivers turn off causing relays SR81 and SR83 to open.This removes all power to the set, except for the standby supply. Because D846 is poweredby the standby supply, the television must be unplugged to reset the latch function. When therelay opens at shutdown, the condition that caused the shutdown disappears. Therefore, apeak-response or min-max meter must be used to test for the momentary cause of theshutdown. A peak-response meter measures and stores the highest and lowest voltage thatoccurs at a test point Product Safety Notice

OVP=Over Voltage ProtectOCP=Over Current Protect

D439

D820D371

D7701

D891

D819

D490

H. Stop 2

H. Stop 1

+15V OVP

+35VOCP

+21VOCP

-21VOCP

+21VOVP

+125VOVP

+125VOCP

TSQSTG004 R1/00

R846

The information contained in this document is for use by qualified service personnel only. Always refer to theproper service manual for the model number of the unit whenever performing service or making adjustments.The use of substitute replacement parts that do not have the same safety characteristics as specified in theparts list may create shock, fire, X-ray radiation or other hazards.

Start.

Remove fusesF863 &F864.

Apply powerto the TV. Do relaysSR81and SR83 Still

disengage?

Remove fuseF804.

Check the +21V OCPand -21V OCP.

Refer to section one.

With F804 still out ofcircuit, remove fuse

F806.

Check the H. stop 1, H. Stop 2, +15 OVP, and

X-ray protect.Refer to section two.

Apply powerto the TV. Do relaysSR81and SR83 Still

disengage?

Apply powerto the TV. Do relaysSR81and SR83 Still

disengage?Check the

125V OVP, 125V OCP,and the +21V OVP.

Refer to section four.

Check the +35V OCP.Refer to section three.

Yes No

Yes No

Yes No

Shutdown Troubleshooting Flowchart 4

Notes: The purpose of this flowchart is to help narrow the cause of shutdown. Refer to the service manual for additional information. With F804 open, the television may power up but not have a picture. This does not mean the television is still in shutdown. Shutdown is indicated by the power relays disengaging and the red power LED blinking at a half second rate. The power cord must then be unplugged and plugged back in to restore operation. Key: OVP = Over Voltage Protect. OCP = Over Current Protect.

Caution: Disconnect power from the television before adding or removing fuses. Always use an isolation transformer when troubleshooting.

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If this flowchart fails to solve the shutdown problem, check the shutdown latch circuit components D846 and Q845