LG 50PT350 bad lower y buffer

[shiz1]

Hello everyone,
Recently received an older lg plasma for free to fix.
Symptoms - no picture but i have sound. I hear the click of the relay, and the hum from the ysus.

What i've tried - i remove the ysus buffers one by one, when i removed the lower buffer i get picture on the top half of the screen. Removing the top buffer and leaving the bottom still gives me a black screen.
i tested the va/vs at the psu and they're within spec as outlined by the sticker.
I tested the lower buffer checking continuity between the white connector - see attached pics - on the buffer and the connectors that attach to the fat wide ribbons on the side. I get continuity at one of the ICs.... so im assuming the lower buffer is toast.

Im uncertain how to proceed to test to check if the damage spreads to the the main ysus itself or if its localized to the buffer.. There has to be a reason why that lower buffer is toast....i'd hate to buy another lower buffer, install it then blow it again...
any help would be appreciated

[dick_barton]

Re: LG 50PT350 bad lower y buffer

It does look as though it would probably only require the lower buffer to be replaced. Having half a screen displayed would suggest the necessary voltages are OK.
See what others more experience forum members have to say.

[shiz1]

Re: LG 50PT350 bad lower y buffer

anyone?

[shiz1]

Re: LG 50PT350 bad lower y buffer

Hey guys, so i replaced the Ysus board...the issues still persist (still waiting on a lower buffer).
However i tried to measure the VSC Vy and im not getting any readings.... I have it set to DC v...but i get no reading when i measure across the resistor for either the vy and vsc on the Ysus

Am i just measuring it wrong?

[R_J]

Re: LG 50PT350 bad lower y buffer

If the buffer board is removed You won't be able to measure the VSC voltage across the resistor, If I remember, you might be able to measure a voltage at the VSC point to ground but without the buffer board there is no voltage drop across the VSC test points (resistor).

[shiz1]

Re: LG 50PT350 bad lower y buffer

If the buffer board is removed You won't be able to measure the VSC voltage across the resistor, If I remember, you might be able to measure a voltage at the VSC point to ground but without the buffer board there is no voltage drop across the VSC test points (resistor).

Ahh good to know. Im assuming the same would apply if your board is pooched.
Ill re-measure once the new board comes in hopefully that resolves the issue