LG 42PT350 Won't Turn On. YSUS Shorted. Bad buffer too?

[johnboy1313]

I opened this one up this afternoon. It wouldn't turn on. Red indicator light at standby. When you power the set on, the LED would shut off for a second them come back on and stay on. The set would never power on. I opened it up and got it to power up with the Y-Sus unplugged. It has the EBR68341901 YSUS board and the EBR68288401 buffer board. I found 3 bad 30f124 and 2 bad IRG71C28U transistors. Will a test for shorts between the connectors on each side work like on a Samsung buffer?

Also, I didn't notice it at first, but the control board has an LED on it that appears to be flashing a code at me. You be the judge.

https://www.youtube.com/watch?v=bKssQwzOeBk

Pics.

[johnboy1313]

Re: LG 42PT350 Won't Turn On. YSUS Shorted. Bad buffer too?

What do you suppose took out the transistors in the first place? Do you think I'll be able to replace just those bad components and get away with it?

[tom66]

Re: LG 42PT350 Won't Turn On. YSUS Shorted. Bad buffer too?

Bad buffer nowadays would rarely cause Y-sus failure. But, the test would be similar. When replacing those IGBTs I'd also consider replacing the driver chip for them.
You could run the Y-sus without those IGBTs in place, then see if you get -Vy and Vsc. If those voltages are OK when the buffers are connected, then the buffers are not bad.

[johnboy1313]

Re: LG 42PT350 Won't Turn On. YSUS Shorted. Bad buffer too?

And if the set powers on, the driver chips are ok?