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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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TDA2579 No Vertical O/P
Hi,
Im working on a NEC TV that has no vertical deflection (white horizontal line). There is no O/P on Pin 1 which is the vertical drive to the deflection amp (TDA3654). I have replaced the TDA2579 chip and still no drive on pin 1. Checked pin 3 with external cap and there is a proper sawtooth waveform there. Pin 2 has about 1.8V on it taking it just short of blanking the sandcastle O/P. Pin 4 (vert def current) appears dead which i assume would be due to no drive to vert amp and then no O/P. I have lifted off pin 1 of the TDA2579 and still nothing. Any idea's to what could be causing this? there is horizontal defelection so chip has to be powered up. Could there being no feedback cause it to have no O/P, therefore the vertical amp possably being dead? Cheers, Shaun |
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