LG 42PC51 plasma problem

[MomirPeh]

Hello, guys!

I have a mentioned LG plasma and I had a power outage during the night. In the morning TV was dead. I narrowed the problem to a mosfet on the power board, replaced it and the TV powered on, but there was a red-white blotch on the screen, pulsating a bit and there were horizontal red lines in the bottom half of the screen. I have found that th YDRV board was toast (two of the chips, in fact) and I replaced it with one from ebay, so the red lines are gone, but the blotch is there... I checked the YSUS and the fuses, mosfets and the hybrid were all ok (no shorts). I also checked the voltages and the only one that was off was the 3.4V_ON line, which was 4.3V. I'm clueless on what to check next or what is my next suspect...

Thanks in advance!

P.S. This is a YouTube video of the problem:
https://www.youtube.com/watch?v=ZRZis8ufU2o

[tom66]

Re: LG 42PC51 plasma problem

The problem on this is probably Z-sus plus Y-buffer.

[MomirPeh]

Re: LG 42PC51 plasma problem

Thanks for reply!

I just checked the ZSUS IPM IC and there were no shorts either. Fuse checks out too.
BTW, ZSUS board is: EBR36921701

[tom66]

Re: LG 42PC51 plasma problem

The IPM doesn't have to short to fail. To rule it out, you can use an oscilloscope. Potentially you can make basic tests with a DMM. Pictures would help.

[MomirPeh]

Re: LG 42PC51 plasma problem

Here are some pictures of the ZSUS board, as requested.

[tom66]

Re: LG 42PC51 plasma problem

Oh, this one is quite different to typical LG IPM boards. You will unfortunately require an oscilloscope to test the output. You can't do it with a DMM.

[MomirPeh]

Re: LG 42PC51 plasma problem

Ok, I will try that during the next week, since I don't have the oscilloscope at home and I will have to bring one from work.
Thanks for help so far.

[tom66]

Re: LG 42PC51 plasma problem

You should check you have a 10X probe (rated for 400V or more) and ideally, the scope should be 400V rated or more (in case you switch to 1X accidentally.)