LG42" plasma

[cornboats]

LG42PQ3000. Standby red to blue. Screen channel identification- full screen for a few milliseconds then Ysus and z sus voltages drop. Sound is there but no picture.

Ysus- -vy from -175v down to 3v

z sus 80v down to 50v

VS, Va and 5v remain.

When I disconnect supply from y sus to z sus Ysus voltages remain up.

When I disconnect Y drive Ysus and z sus voltages remain up.

I thought it could be the Y drive board but I've had 2 boards from different suppliers

with no difference to the outcome. Does anyone know the best way to check the Y drive board in case I've been sold duff boards?

I'm loosing my patience with this one so any help or advice please.