LG Plasma 50PS11, No picture but still has sound

[TArmstrong]

Hello,

Just looking for some diagnostic advice for my 50" LG plasma, since i'm too cheap to buy a new TV.

TV has a lot of hours on it, recently the picture stopped working but the sound still works. I have browsed these forums and some youtube channels and started some diagnostics.

So far I have tried running the board with the Y-Sustain disconnected, upper Y drive disconnected, lower Y drive disconnected and the z sustain board disconnected.

There was no picture in any of these cases and I have power on both sides of the fuse on the Y-Sustain and Z-sustain boards.

Any suggestions on what I should check or measure next to isolate the problem?

[ReeceyBurger123]

Re: LG Plasma 50PS11, No picture but still has sound

Help us help you, upload images and voltages that you have tested first !

[TArmstrong]

Re: LG Plasma 50PS11, No picture but still has sound

See attached pics.
1st pic is Ysus VS+
2nd pic is Ysus VA+
3rd pic is a closeup of Y sus power input?
4th pic is Ysus +5V
5th pic is Zsus VS
6th pic is Zsus +5V

Any ideas what I should check to help isolate the issue?
Thanks for the help.

[TArmstrong]

Re: LG Plasma 50PS11, No picture but still has sound

I measured VZB (tough to tell where to measure) on the zsus board at 112 V. This doesn't match any voltages on the pan sticker.

Would this point to a bad zsus board?

[Jeff Pepin]

Re: LG Plasma 50PS11, No picture but still has sound

I have fixed 2 of these at this time this week but one give me headhashes now im about to post a thead about it

If you are lucky this resistor transformed himself into a powerfull toaster and opened (check attached pictures ) it look like a very common failure i got it on 2 of 3 y sustain . To prevent that this one blow again i replaced it by a 5watts ceramic resistor , the value is 2.2 ohms

[Jeff Pepin]

Re: LG Plasma 50PS11, No picture but still has sound

The second one that give me headhashes the resisstor was fine , but i have found 2 fets labeled "45F122" dead but not shorted located on the center heatsink of the y sustain

Is a lot of work but you need to remove entire heatsink with fets on it , after that you can test each one by put your dmm in diode mode and placing your red probe on left pin , black probe on center pin to charge the gate, then immediately put the red probe on the center pin and the black on the right pin you should have a reading that prove that it switched on

Then , leave the red probe on center pin and go toutch the left pin with your black probe to switch it off , now put again your black probe on the right pin and you should read O.L , replace it if it show no signs of life

[ReeceyBurger123]

Re: LG Plasma 50PS11, No picture but still has sound

Ive also had a very little fet that drives the transformer in the lower right hand corner covered in glue fail shorting the 5v rail on Ysus.