LG RZ42PX11 Flickering / Flashing

[dragometin]

Hi.

TV: LG RZ42PX11
Type: Plasma

I have this old plasma that it's working fine. But it has a strange issue. If the picture is white, or has strong colors, it will flash and flicker. I attached a video showing the issue.

What could cause that?

Thank you.

[dragometin]

Re: LG RZ42PX11 Flickering / Flashing

Can someone help me?

[Biruslapio]

Re: LG RZ42PX11 Flickering / Flashing

This TV is really old, this problem could be caused even by dust on the connectors, could you take the TV back off and see if there's excess of dust in it? If not, you need a multimeter to measure some test points for important voltages of the TV, are you familiar with that? Look for bulging capacitors on the boards.

Is the sound always working even with the flickering?

[dragometin]

Re: LG RZ42PX11 Flickering / Flashing

Yes. The sound is always on and working nice even with the flickering.

I'm very familiar in working with electronics.

I took the back cover off, and checked the voltages to the sticker on my panel: Vs: 190v, Va:65v

Vs: Was 187v, so i adjusted to 190.1v and it's now better but it still flickers a little bit.
Va: Was 65v, OK.

Other Voltages:

VSCW: 115v
-Vy: -90v
VSetup: 219v

NO bulged capacitors were found in all boards.

BTW, it's a PDP42V6 screen

[dragometin]

Re: LG RZ42PX11 Flickering / Flashing

Yes. The sound is always on and working nice even with the flickering.

I'm very familiar in working with electronics.

I took the back cover off, and checked the voltages to the sticker on my panel: Vs: 190v, Va:65v

Vs: Was 187v, so i adjusted to 190.1v and it's now better but it still flickers a little bit.
Va: Was 65v, OK.

Other Voltages:

VSCW: 115v
-Vy: -90v
VSetup: 219v

NO bulged capacitors were found in all boards.

BTW, it's a PDP42V6 screen

Adjusted Some voltages. Still flickers and no voltage change while flickering.

VSCW: 115v , Adjusted to 115v
-Vy: -90v , Adjusted to -80v
VSetup: 219v, Adjusted to 200v

[Biruslapio]

Re: LG RZ42PX11 Flickering / Flashing

When the flicker occours, use the multimeter on VA and VS, they should be stable, then VSCN, -VY and VSetup.
If VA and VS are not oscillating more than normal with the flickering the power supply is not to blame, when the screen turns white it's normal for them to drop 1 or 2 volts.

Does it flicker on cold boot with a white screen? Or only when it's hot? On that video, was it losing the signal also and displaying channel information and going into menus by itself? If then it could be bad mainboard solid capacitors.

[dick_barton]

Re: LG RZ42PX11 Flickering / Flashing

Looking at the video it does appear to be losing the video content intermittently.
Generally I would run a self-test but I am unfamiliar with your set. Do a search on the forum for information on running the "self- test" with the mainboard disconnected from the logic board. Hopefully your set will have this function.

[dragometin]

Re: LG RZ42PX11 Flickering / Flashing

Thank you for all your replies.


All voltages are rock solid when the ficker ocurrs, even the 15v supply on the Y Board.

I found out that if i follow the sticker voltages it flickers a lot, so i reverted VSCW, -Vy and VSetup voltages back to "factory default". So the only adjustment I made was the Vs from 187v to 190v.

When it's cold it flickers when displaying strong colors, when it's warm it flickers but it's with less frequency.

That channel information was actually me with the remote trying to get some white colors into the picture to make it flicker for the video, so no worries on the main board. I replaced the main board because the analog inputs where not working. And yes it also flickers with the old main board.

I'm aware of the green dot's issue with this chassis.

BTW what does the SET_UP and SET_DW potentiometers adjust on the Y board?

[Biruslapio]

Re: LG RZ42PX11 Flickering / Flashing

SET up/down are for adjust the final picture of the tv, they come calibrated from factory for each display, it messes with the black levels, if you adjust them off the optimal point it will increase image retention on the panel and introduce random pixels on white and black backgrounds.

At this point, maybe the logic board is going bad, or some capacitors (these solid capacitors do not bulge, they dry and stop working properly), cold soldering joints on Y-SUS or Z-SUS, notice anything on visual inspection?

On Z-SUS there is one trimpot for adjusting probably Z-BIAS, but there is no Z-BIAS test point provided nor voltage information on the panel sticker.

Can also try slowly increasing or decreasing -VY, VSETUP and VSCN one at a time and see which one affects the flickering the most.