I have an LG plasma that after reading through a bunch of posts and doing some testing I believe has a bad YSUS board. The problem is that that doesn't make sense to me for some of the symptoms. The problem started yesterday. While watching a movie the TV just shut down like I pressed power. I have it hooked to a PC and use RS232 to turn it off and on so I thought maybe something had glitched there. I turned it back on and finished the movie with no problems. The same thing happened today so I checked logs to see if something in the control glitched and sent an off command but it didn't, After messing around a bit it shut down and wouldn't turn on. I unplugged it and plugged it back in and noticed a hum that sounded a lot like a cap failing so I pulled the back and found that the hum was coming from YSUS. At that point I started searching and testing. The test pattern jumper test didn't produce anything. The VS, VA, and 5v are all testing within the specs printed on the power supply board but the VY test point only read 1v and the VSC .25v, which if I understand correctly indicates a failed YSUS. The part that doesn't make sense to me is the random powering off. That seems like it would be more of a power supply or main board issue. I had the solder joints crack on one or both(can't remember) of the sustain boards about 5 years ago and took some other components out but the symptoms of that failure were totally different, just impacting the picture quality. I'd love to know what caused the power down but if someone could help me confirm the YSUS diag that would be great.
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