TELEVISION TECHNICAL BULLETIN - CTV 2004 03 03 - East/west faults

Oct 12, 2026

Television technical bulletin CTV 2004 03 03 (Revision-3) provides fault-finding and correction guidance for east/west stage issues on model 66GS62H. It explains how Q602 must be enabled during flyback to supply voltage to Q601, how startup lacks correction, and how the driver and control timing from the microprocessor affect scan and correction. It outlines checks for Q602 drive circuitry, IC 1001 waveform/parabola behavior, EEPROM blanking, potential faults in the line output transistor, common SMD diode failures, and causes of large-picture symptoms, plus production circuit changes and component updates.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages4

Reading Time10 min

AccessFree to download

East/west faults

Q602 control and flyback operation

Startup behavior and gate drive

Drive-circuit testing steps

Line output transistor dependency

IC 1001 and EEPROM checks

SMD diode and driver transistor failures

Large picture and leaky Q602 causes

Changes to the circuit during production

TELEVISION TECHNICAL BULLETIN CTV 2004 03 03 Month of Issue: 22nd July 2004 Classification: White Page 1 of 4 MODEL 66GS62H East/west faults Faults in the east/west stage of this set can be complicated to find due to the type of circuit being used. A problem in this stage can also lead to a dead set. It is recommended that when fault finding in this area , to follow the guidelines given below. Note that as this part of the circuit operates during the flyback period , it is very difficult to ‘scope’ any waveforms. The east/west control transistor (Q602) has to be turned on to provide voltage to the collector of the line output transistor (Q601) , without this voltage , the line will not come up. During the flyback period , the on time of Q602 is varied to give more or less scan and therefore east/west correction. The timing of this is critical and is controlled by the microprocessor. When the set starts up , there is no east/west correction; therefore Q602 will not be turned on. As Q602 needs to be turned on , there is a small circuit that provides this function. R638 (100k􀀁 ) is connected to the +5V line which connects to the gate of Q602 via R657 , D607 , D604 , D617 , R612 and R616 , pulling it high and turning it on at start up. When theset is running , the east/west control signal keeps turning Q602 on when necessary. If it is suspected that there is a fault with the drive to Q602 , not allowing it to turn on at start up , short out the source to drain of this device and turn on. Note that the picture will be extra large when this is done. The next step is to see if the driver circuit is faulty. Disconnect R657 ( D616 end) and apply 2.5V from a DC power supply to this end. When the set is turned on , it should start up. If the voltage is varied between about 1.5V and 4.5V, the width should vary. If it does not there could be a problem with the drive circuitry. Another component that will cause this fault is the line output transistor. If it has been replaced with a BUH515 , the flyback pulse will not be high enough to provide any east/west correction. It is therefore very important to ensure that a BUH515D is used in Q601 position. This device must be ordered from Sharp Parts Centre as it has been known for transistors supplied from other sources not to work , or work incorrectly. If the driver stage appears to be alright, examine the waveform on pin 99 of IC 1001 , this should be a parabola at 50Hz; this will change as the east/west controls are adjusted. If there is no waveform, or it does not adjust, blank the EEPROM (IC 1003) using the appropriate jig (see the Memory and Processor Technical Bulletin for the 66GS62H) . If this does not restore the output from IC 1001 , suspect IC 1001. Note that the type of IC 1001 depends on the size of the EEPROM fitted-see The GA10 Parts Technical Bulletin for more details. If the waveform changes when adjusted , then the output circuit is probably faulty. When fault finding in the east/west drive circuit, it is often found that one of the SMD diodes is faulty, normally caused by failure of Q602 . When replacing Q602 be careful not to accidentally wipe R610 off the board. R610 is in the control circuit and if it is missing , Q602 will never turn on. It is possible for any of the three driver transistors to fail (Q603 , Q604 and Q608) . It is recommended that if any of these transistors are suspect that all three are replaced together. Large picture For a large picture or east/west problems (sometimes can occur after replacing a short circuit line output transistor) can be caused by Q602 going short circuit or leaky. Also ensure that C601. C602 , C619 and C624 are not dry jointed or faulty in any way Sharp Electronics ( UK) Limited Reference AvW 10 03 2004-3 Revision-3 White – Carry out as required Yellow – Carry out as required and whenever the unit comes in for service Red – Carry out on all units TELEVISION TECHNICAL BULLETIN CTV 2004 03

FAQs

Why can east/west faults be difficult to find on this circuit?

The east/west section operates during the flyback period, making it very difficult to scope waveforms.

What prevents east/west correction at set startup?

When the set starts, there is no east/west correction, so Q602 will not be turned on; a small circuit provides the function at start up.

What should be checked if there is no waveform adjustment on IC 1001 pin 99?

Blank the EEPROM (IC 1003) using the appropriate jig; if output from IC 1001 is still not restored, suspect IC 1001.

Oct 12, 2026

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