50PG6010 (LG 50" trouble diagnosing problem)

[Hamie]

Hello all

This tv is confusing the hell outa me!
Power board - voltages ok.
X - voltages ok
Y - voltages ok

But no picture whatsoever!
I'm guessing that the logic board or the small control board are at fault but how do I determin what one?

Any advice would be greatly appreciated.

Any further pictures needed please ask.

Thanks

[audiofreak19]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Does the tv have sound. Or you turn it on and no picture and no sound.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

I don't know if it has sound, I'm unsure if it's freeview is tuned in or what input is selected when It starts up.

[Alastair E]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Normaly IF set is on, and you plug in a SCART from a Freeview-box--thats on and tuned in, the set --should--switch to that and give sound....
--Doesnt always work, but worth a try.

When you say the X voltages and Y volts are all OK, Does this include the -Vy and the other voltages indicated on the Y-SUS?

There's more voltages on the Y-SUS, and Z-SUS than just the Va and Vs supplies--If one isnt there, set wont give any pictures....

A fairly common issue is for a Buffer to fail and drag down the -Vy supply.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Ok well I've checked all the voltages leading to the lower buffers and they are all fine.
Where else should I be checking.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Also checked the ohms on the black connections between the ysus and ybuffer
Mostly all reading 268 kohms.
What other tests can i do to exclude this board?

[tom66]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

You've checked the -Vy and Vsc voltages?

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Ok there are no test points on the ysus.
There are 2 resistors marked xy and vsc

The xy comes in at 53v

Vsc is 54v

[tom66]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

-Vy should be around -180V, Vsc around 150V. Exact ratings on panel sticker e.x.

VS: 201V VA: 60V
N.A. / -Vy / Vsc / N.A. / Vzbias

Remove the buffers and repeat; if the voltages come back you have a bad buffer.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Thanks tom,

Ok unplugging the buffer board the voltages have actually dropped??
Now reading 10v roughly.... I'm guessing that means bad news for the y-sus then! :-(

Out of interest why would they drop rather than increase?
Doesn't make sense to me :-/

Thanks

[tom66]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Could be biases through the buffer causing the voltage to change - either way it is a bad Y-sus. I think some of these have a 4-component repair kit available to fix issues with the Y-sus but I'm not sure what's in it. I know it applies to 42PG3000 although the Y-sus is totally different.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Thanks again, I'll check for shorts tomorrow and look into the repair kit.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Ok so turned out one of the resistors had shorted.
R311 if memory serves me right.

So tv almost working.... Almost!
Now showing around 3/4 of the screen.



So I've unplugged the Ysus and I get no picture but sound still ok.... Does this mean the X is ok?

I'm taking a guess the lower left hand buffer is bad.
Any tests I can do to confirm this?

Thanks

[tom66]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Check the ribbons are installed properly, remove and replace them.

Check the Va feed for that part of the panel is connected. (May be a small cable coming off the Z-sus board, or connecting between the X-address boards; the ones on the bottom of the panel.)

IMPORTANT!!! Disconnect the TV power for 5 minutes BEFORE fiddling with the Va voltages or connectors as failure to do so will likely kill the panel! Do NOT adjust while set is powered on.

[Hamie]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Hello tom,

I checked the va 64v
And so seems ok.
Reset all the ribbons, and went white with a black line.
As below.

[baddesley]

Re: 50PG6010 (LG 50" trouble diagnosing problem)

Hi Guys,

I also have one of these sets with a similar problem. I have had it for over a year now and it worked fine for all that time (once I'd replaced the four 3300mf caps on the PSU anyway).

Recently though, it delveloped a fault with the PSU, failing to come on, but while trying to sort that out, the PSU blew up, taking the Y Sus with it.

Initially, I replaced the PSU, which now works fine, all voltages present and normal, but got no picture. It was then that I found out that the Y Sus was faulty (a couple of blown FETs and a SM fuse at least), but rather than replace these, I bought a tested replacement board from the same people that I'd got the PSU from.

However, despite it seeming to run OK (all fuses intact and all heatsinks running nicely warm, including those on the buffer boards), there is still no picture. PSU runs quietly and the sound is fine. I tried to measure VY and VSC on the board, but on DC 600V range (highest on my DMM), it goes off scale. Is this normal?

The X Sus heatsinks are cool though, despite power being on the board and all FETs/Transistors and Fuses checking out OK (cold checks with DVM), so to my mind, this is not being driven at all - though my knowledge of plasmas is very limited (I'm an old-school ex - CRT TV & general Electronics Engineer).

I have tried disconnecing the lower driver L & R boards, but no difference. Any ideas, as this is driving me nuts too and I have not been able to get any circuit diagrams (downloaded the supposed service manual, but that has very limited low power only circuits).

Any advice or ideas much appreciated. Thanks in advance.