lg 50pg3000 sound but no picture

[wreksta]

hi a got this set in today checked vs va etc all fuses mosfets etc are all fine
has a green signal light on the ldvs board when turned on I get sound just no picture no glow on the screen nothing

any ideas

[newtothis]

Re: lg 50pg3000 sound but no picture

Does the standby light come on? if so what does it do?

[wreksta]

Re: lg 50pg3000 sound but no picture

normal standby light press power goes green and stays green get sound but no picture

[tom66]

Re: lg 50pg3000 sound but no picture

Try unplugging LVDS cable and placing jumper across EXT AUTO GEN.

[wreksta]

Re: lg 50pg3000 sound but no picture

with auto gen jumper jumped I still get no screen it don't light up and defo no picture

[tom66]

Re: lg 50pg3000 sound but no picture

[posted in error]

[wreksta]

Re: lg 50pg3000 sound but no picture

yes mate I get nothing

ive checked all fuses all voltages and everything checks out

mosfets are all fine as are the diodes do you know where I can find the pg3000 training slides that's will have a load of info that might be able to help me in my fault finding

I also tried disconnecting to and lower buffer on the y side and tried running like that but to no avail

[tom66]

Re: lg 50pg3000 sound but no picture

You have Vs and Va? What do you have on -Vy and Vsc? What about Vzbias?
On back of LG PDP module is something like LG PDP50K1##### what is the exact code for your model?

[wreksta]

Re: lg 50pg3000 sound but no picture

hold on mate whats the vzbias

[wreksta]

Re: lg 50pg3000 sound but no picture

pdp50g1
aalso where to measure vsc vzbias ets cant see nothing on the board

[tom66]

Re: lg 50pg3000 sound but no picture

This manual covers PDP50G1.


It indicates where to check all mentioned voltages.

[wreksta]

Re: lg 50pg3000 sound but no picture

-Vy 0v

Vsc 0v

so y board seems to be at fault

Vzbias 97.6 normal according to panel should be 98 so the z board seems okies but never gets hot on the heatsinks

[tom66]

Re: lg 50pg3000 sound but no picture

You will not get any heat from heatsinks if there is no power (no light) being pumped into the plasma panel.

Check fuses on Y-sus, obvious burn marks, etc.
Isolate buffer board(s) and check if the voltages rise without them in place.

[Scotttait]

Re: lg 50pg3000 sound but no picture

I have this same issue. I think mine started from a faulty buffer
Board. Is this possible?

[wreksta]

Re: lg 50pg3000 sound but no picture

al voltages read correctly after I have removed the buffers

195 and 135 on the vy and the vsc

now how to test this type of buffer board


I have tested these resistors on diode setting I get 0.6.0 on my meter but the continuity crackles on them that means there bad don't it they are marked 470

[tom66]

Re: lg 50pg3000 sound but no picture

No point testing them, the fact that the voltages come up means your buffers are bad. You can try one at a time if you want. You may get half a picture.

[wreksta]

Re: lg 50pg3000 sound but no picture

I want to try repair it tom ive removed the heatsinks and the main microchips look fine no burns or anything

[tom66]

Re: lg 50pg3000 sound but no picture

Generally I wouldn't say it's worth it.. you may be looking at a cascading failure that has killed several buffer chips if more than one board is bad. I see both boards available for £85 new, they may be much cheaper if from a scrapped TV.

But if you were to repair it, you'd need to look and see if the individual buffer ICs are available as replacement parts, if not, there's not much chance of repairing them.

Those diodes are just for the -VSC circuit, to limit addressing current. The only parts I'm aware that can cause this fault are the buffer chips.