LG 42PC1DA Plasma Sound but blank screen

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

OK, across any of the 5 red capacitors (bottom left) you should have around 60-100V if the Z-sustain is working.

[ghiotom]

Re: LG 42PC1DA Plasma Sound but blank screen

Are you sure you're getting 15V at the IPM on the Zsus board?

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

There's 162v across the 5 x capacitor bank.
15v is getting to the Z-sus IPM.

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

Hmm, 162V seems too high, what is Vs for this set?

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

VS 186v; VA 60v

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

I suppose, as it is not at full Vs, or 0V, that it is not shorted out, but I am really confused by why you don't have any picture at all. Apart from the ramp wave on the Z-sustain everything appears OK.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

Could it have anything to do with the X-Board?

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

Do you mean the Z-sustain or the panel X buffers? It's unlikely to be the panel X buffers, as they usually cause stuck lines or blocks of pixels when they fail.

[ghiotom]

Re: LG 42PC1DA Plasma Sound but blank screen

Even with the Zsus board disconnected, you should get a dim image on the screen.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

Yes, I did mean the X buffer board.
Even with the Z-sus board removed the screen is completely blank.

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

This makes me worry the panel is bad. Is it making a buzzing/crackling sound, like someone rapidly tapping on glass?

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

I was beginning to have the same thought myself. However, there is no sound coming from the panel.

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

Either way something isn't right with the Z-sustain and I'm not sure why.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

If the panel has gone would that cause the Z-sus board to be cold but the Y-sus board warm as normal?

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

Normally neither board would be warm.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

So is the X-sus board getting warm a sign the panel is OK?

[ghiotom]

Re: LG 42PC1DA Plasma Sound but blank screen

Have you ruled out the Y-Buffer board? If all of your DC voltages are correct and you have the correct waveform coming out of your Y-Sus board, could the buffer board be the problem? BTW, I have a working 42PC3D, which is similar to yours, cracked open on the bench in case you need me to make any comparison checks.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

I assume the Y-buffer board is the long board on the left (sometimes called the Y-drive board)?
If that's the one, it has 10 x scan ics which would all have to have failed to leave the screen blank wouldn't they?
How can I test the Y-buffer board?

[tom66]

Re: LG 42PC1DA Plasma Sound but blank screen

This link has a test you can perform:
http://blog.coppelltvrepair.com/2010...er-boards.html

It's for a Samsung but it should be similar for LG.

[LesWoollam]

Re: LG 42PC1DA Plasma Sound but blank screen

Performed the test on the buffer board and all scan chips check-out OK. However, on listening very closely to the screen I can hear a faint buzzing sound - certainly not like glass being tapped, but nevertheless there is a buzzing sound. Sounding like a dead panel?