green dots on plasma tv set

:Hi, I have gained one LG based Plasma TV set. :This TV is maked around model 42V5 chassis. :In dark scenes, I see high quantity of green dots that is very numerous :immediately after brightness change from light to dark, then decreases :if scene persist dark. :How I can check? :Thanks and excuse me for my english. : :Bye.

Back a few years LG plasma 42 inch TV's suffered from a "green line" symptom. Usually off to one side (can't remember which side) a thin vertical green line stretched from top to bottom and as it worsened an additional parallel green line would start to appear.

The only solution is a replacement of the plasma display.

I had an old war veteran friend who paid about $4000 for one of these sets and he had owned it for about 2-1/2 years (long past the warranty period) when it developed the symptom. After giving LG a good sob story they agreed to replace the plasma screen at minimal cost (about $200). The real repair cost was well over $1000, which he could definitely not afford. Repairing the set allowed him to sell the set for $1000 but otherwise it was not worth a bean.

Sounds like a Vs adjustment...

Mark Z.

Mark Zacharias ha scritto:

thanks, I try. how I can adjust Vs? and how much voltage? I have not schematics...

bye.

Ross Herbert ha scritto:

thanks, but I have green dots, not green line on my display.

Seconded ...

Arfa

Usually just below 200 volts; adjust to lower the voltage until the speckes disappear. If no change, return the adjustment to it's original position.

Just exactly where this is located in your unit I don't know. In Samsung models it is usually in one corner of the Y main board, near a Vs test point.

Mark Z.

On Sun, 22 Mar 2009 11:05:07 -0500, "Mark Zacharias" put finger to keyboard and composed:

Ditto.

The Serviceman column in the April 2009 issue of Silicon Chip Magazine identifies the problem as a V Setup adjustment. FWIW, on the PDP42V72462 chassis it is VR1 on the Y Sus board.

- Franc Zabkar

Franc Zabkar ha scritto:

Thanks to all. If Vs and VR1 adjustment does not solve the problem, is it possible that this is an electrolytic capacitor failure?

Thansk.

Anything's *possible* I suppose, but in this case, I would say that it's pretty unlkely. The symptoms you describe are very typical of mis-adjustment of Vs, and I would give correcting that, a better than 90% chance of success ...

Arfa

Arfa Daily ha scritto:

I have tryed to adjust Vs. In back of panel there it is a label that says: Vs=190V

I tried up to 195V but green dots does not disappears. I also tried to adjust under 180V, and green dots decreases, but together with screen brightness and detail...

If not capacitors, how I can try?

Thanks.

Probably the PDP not erasing the pixels fast enough. If this is the case the only way to repair is to replace the PDP.

This set is made by Hyundai.

I agree at this point - an aged panel.

Mark Z.

Agreed also. The clue is probably that it gets better as Vs is turned down, but not before the picture starts to deteriorate ...

Arfa

Arfa Daily ha scritto:

yes, picture panel has several work hours, but I not remember that green pixels was already present before IPM fail. This is a common defect due to aging? (I never put hands in plasma tv set) I have checked ripples to Vs line with oscilloscope ac coupled, and I see most spikes (about 3-4Vpp)... for this thought about the capacitors.

conclusions?

Thanks.

Too bad you don't remember, this would help immensely.

My conclusion is this is a classic case of an aged panel in need of replacement. You might want to research how plasma develops an image to give you a better understanding of how age affects the process. I doubt that 3-4Vpp noise in the Vs is responsible but I could be wrong and would be happy if I were wrong given the cost of a new PDP. If time is not a factor you could ESR some capacitors in the Vs and try to eliminate the ripple.