LG Plasma 50PK540-UE

[pc_doc_al]

Screen is Red and Black. You can see the source playing behind the red and black. Sound works. Picture attached.

[tom66]

Re: LG Plasma 50PK540-UE

Looks like a Y-sustain failure or Y-buffer failure to me. I'd try checking Vsc and -Vy voltages on Y-sus to see if they're good.

[pc_doc_al]

Re: LG Plasma 50PK540-UE

Could you instruct me on the proper way to check those voltages?
Thanks

[tom66]

Re: LG Plasma 50PK540-UE

You need a digital voltmeter.

Set the meter on volts DC, if manually ranging 600 or 1000V DC.

Measure the voltages and note them down.

On the back of the plasma display panel, inside the unit, is a sticker marked LG Electronics, country of origin (China, Korea, Mexico, Hungary) and "PDP50R1" for this model. You want to look at the voltages on this sticker. Typical order is N/A / -Vy / Vsc / N/A / Vzb.

They should match within approx 2V.

[pc_doc_al]

Re: LG Plasma 50PK540-UE

The voltages going to the Ysus are spot on with label.

[tom66]

Re: LG Plasma 50PK540-UE

OK, do you see Vzb on Z-sus? Test that, too.

[pc_doc_al]

Re: LG Plasma 50PK540-UE

Readings
Va : 59.6v
vs : 201.9v

Ysus
Vy : by the + marking 95.4v
Vy : by the - marking 93.3v

VSC : by the + marking 2.2v
VSC : by the - marking 95.4v


Zsus
VZB 114v

picture is attached to show the "+" and "-" markings I'm referring to.

[tom66]

Re: LG Plasma 50PK540-UE

You should measure across the + and - not go to the chassis.

[pc_doc_al]

Re: LG Plasma 50PK540-UE

Ysus
Vy: -188.5v
VSC: 150.2v

Zsus
VZB: 113.9v

[tom66]

Re: LG Plasma 50PK540-UE

If those match the sticker, they look fine.
If you turn the Vset_up and Vset_dn controls, do you see any improvement in the image?

[pc_doc_al]

Re: LG Plasma 50PK540-UE

Adjusting the set_up & set_dn both affect the color/darkness of the picture, but neither help the clarity.

picture attached.

[tom66]

Re: LG Plasma 50PK540-UE

It is very hard to tell. I think it may be a Y-buffer or Y-sustain problem but I do not know. The only way to be sure is test the Y-sustain output using an oscilloscope.

[pc_doc_al]

Re: LG Plasma 50PK540-UE

Thanks tom66! I replaced the Ysus and the tv works beautiful.

[tom66]

Re: LG Plasma 50PK540-UE

Glad to hear!