Samsung HP-R4252 42" Plasma No Picture

[RobPhotoPro]

No picture symptom on this plasma TV suggested a problem with Y-sustain board and Y-buffers. It features problematic LJ92-01203A / LJ41-02761A and LJ92-01202A / LJ41-02760A with 6 ICs. I checked out Coppell Repair Blogs and some threads here, that helped me to identify shorted buffer and a shorted power FET.

I replaced a shorted lower buffer and one bad IXTA36N30P power fet under the heat sink on the Y-sustain board.

The TV still powers up and stays on with NO picture. I even tried connecting one buffer at a time - no half picture. Checked the voltages, Vscan is present and stable with Y-sustain connected or disconnected. Nothing is getting hot, both Y-sus and Z-sus are making a normal "hum". Ve for Z-sustain present and stable.

I checked the Y-sustain board's main IC - no shorts. The fuse was also fine.
Output voltages to Y-buffers are around -71V.

Looks like something else might go bad on Y-sustain board. Any ideas?

All suggestions very appreciated!
Thanks,
Rob

[PlainBill]

Re: Samsung HP-R4252 42" Plasma No Picture

Forget about it. That -71 volts indicates there is another problem. As indicated, these are problematic. By the time you replace all buffer ICs and the Y-sustain you have spent the major part of the cost of a new 42" plasma TV.

PlainBill

[RobPhotoPro]

Re: Samsung HP-R4252 42" Plasma No Picture

Well, I was lucky to get a replacement lower Y-buffer board from E-bay for $ 36.00, shipping included. The upper buffer tests okay.

So the only problem seems to somewhere on Y-sustain board. I replaced the shorted FET and the main IC tested okay. What else does usually go bad on this board? How can I test the board to make sure, the problem is not somewhere else? Too bad I don't have a similar, working TV to test the boards.... :-(

Thanks,
Rob

[RobPhotoPro]

Re: Samsung HP-R4252 42" Plasma No Picture

This is, how I tested the main Y-sus IC:

http://blog.coppelltvrepair.com/2011...s-ipm-for.html

My IC passed all tests okay.