LG 50PC1D Recurring Ysus Buffer Short

[alanos313]

Hi,

I have an LG 50PC1D plasma TV which suddenly lost picture, showing only an entire screen of moving coloured vertical lines. After a bit of research online, I found a post here http://blog.coppelltvrepair.com/2010...-lines-in.html which pointed to the YSUS buffers, specifically the MOSFETs which are mounted on them... I tested them as per the instructions on the page, and found two shorted FETs on the lower buffer. I replaced them, and the set worked perfectly, without any faults at all. For 30 minutes. Then the same problem returned.

I checked the buffers again, and found that the third FET on the lower buffer had now shorted. So I replaced that one. Again, the set was perfect, this time for about 4 hours. Then it developed a thin vertical line on the right side of the screen, top to bottom. About 30 minutes later, another line appeared, on the left side, top to bottom.

Around 30 minutes after that, the screen began to flicker on and off in roughly 1 second intervals, which is what happened just before it blew the FETs last time! I switched off and allowed it to cool down.
I haven't checked yet, but I'm pretty sure I will find another shorted FET. Can anyone tell me what I can do to trace the cause of these shorts?

Cheers

[capkid]

Re: LG 50PC1D Recurring Ysus Buffer Short

It sounds like your Y-Sus may be faulty. Check your voltages, including VS, VA, VSC, and -VY.

[Tvbob]

Re: LG 50PC1D Recurring Ysus Buffer Short

Change the board The FET is being turned on too long or it is working in to an abnormal load that you won't find with a volt meter.