ZSUS trim pot adjust -LG 42PC3D-

[120volts]

Hello people,

One of my latest picks LG plasma weak dim picture.
I replaced 9 swollen caps on PS board and no difference in picture.
On further investigation I found the ZSUS amp to be shorted.

I bought a used ZSUS and noticed it has a trim pot on it and I'm not sure if I have to set it.

Any help is very appreciated.

[tom66]

Re: ZSUS trim pot adjust -LG 42PC3D-

The panel sticker contains a voltage list e.g.

N.A. / 140 / -180 / N.A. / 87

The last number is Vzbias. That is what you should adjust the pot for.

To check Vzbias, you probe across the resistors marked with Vzbias arrows.

[120volts]

Re: ZSUS trim pot adjust -LG 42PC3D-

Thanks tom I see the arrow for the Zbias

[Alastair E]

Re: ZSUS trim pot adjust -LG 42PC3D-

Check the voltage from ground/chassis to the tab of that transistor, This is the Vzbias voltage--set to what the panel sticker says with the pot on that sub-board.....

[120volts]

Re: ZSUS trim pot adjust -LG 42PC3D-

Should the bias on the YSUS also be set to the same voltage?

[tom66]

Re: ZSUS trim pot adjust -LG 42PC3D-

No, there are two separate adjustments Vsc and -Vy that must be checked:

Negative voltage is -Vy, positive is Vsc. Measure across the resistors/capacitors labelled.