HP PL4260N worth looking at? (photo inside)

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Don't have much experience with plasmas, please estimate chances of this to be repaired.

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Re: HP PL4260N worth looking at? (photo inside)

Attaching better photo.
Has sound.
Y-Sus has been replaced to (probably) working board. Before that it was just black screen.

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Re: HP PL4260N worth looking at? (photo inside)

found burned chip in the Y buffer board.
do you think replacing just the buffer board is enough?

[Andrew F. Ali]

Re: HP PL4260N worth looking at? (photo inside)

Upper or lower buffer Bd? I would look at both Bds. and probably replace them. If you work the TV too long in that condition you may burn out and damage the Y-SUS Bd.

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Re: HP PL4260N worth looking at? (photo inside)

This TV has single Y-buffer board

[Andrew F. Ali]

Re: HP PL4260N worth looking at? (photo inside)

I would replace the single Y-buffer Bd. if the replacement Bd. is affordable.

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Re: HP PL4260N worth looking at? (photo inside)

Replacing the Y-Buffer fixed the TV

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Re: HP PL4260N worth looking at? (photo inside)

Well not completely fixed.
I now noticed fuzzy red-greenish color spikes (starts after ~20 minutes, mostly on white parts of the image)
See video and pic attached
https://photos.app.goo.gl/TZb6VJFiNDgyFsMx2

Should I check caps on the power board or this is some known plasma specific problem?
I suspect power board because I checked the Vs and Va voltages with multimeter and could not get a stable reading. Voltages fluctuate.
Did not notice any bulgy caps though.

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Re: HP PL4260N worth looking at? (photo inside)

Checked Vs with a scope and ripple level is at maximum 3-4v, varies on the picture
Vs is 188v so it is around 2%
And it does not change over time. so I guess this is OK.

Looks like something warms up and causes the problem.
Any idea how to isolate the issue?

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Re: HP PL4260N worth looking at? (photo inside)

I figured out that if I measure Vs and Va across GND wire on the PSU and not the chassis it works fine. Voltages are very close to expected 188 and 60v: 187.5 and and 59.9
I also noticed that the panel mentions other voltages: -200, 120, 100
Where do I check these?
Can't find any test points on the Y-sus board (attached)

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Re: HP PL4260N worth looking at? (photo inside)

OK I leanred that
188 / -200 /120 / N.A / 100 on the PDP means
V SET_UP / -VY / VSC / n.a. / Z_BIAS

I found test points for Vsc and -Vy but my multimeter is not able to measure the voltage. It just reads random like before when I tried to measure Vs and Va across chassis.
I have a cheap harbor freight cen-tech multimeter, but it worked fine for other TVs.

[R_J]

Re: HP PL4260N worth looking at? (photo inside)

It could be the meter, I have an LG meter that will show over voltage when checking some ysus voltages, but the fluke works fine. Vsc looks like its measured across C51 and -Vy is checked across R36 and not to chassis ground in case thats the way you are checking them.
You could try adjusting setup & setdn slightly and see it that removes the speckle. mark the control positions before so you can return them to original if it does'nt help

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Re: HP PL4260N worth looking at? (photo inside)

I swapped the Y-sus board to the original one and found out that it works, but the same problem persists.
Ordered Brymen Multimeter.

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Re: HP PL4260N worth looking at? (photo inside)

New multimeter was able to read correct voltages and they were all fine. I adjusted it to perfection but it did not help.
Any other ideas of what could be the cause of that color fuzz?
It only shows up after about ~20 minutes.

[tom66]

Re: HP PL4260N worth looking at? (photo inside)

The colour fuzz is caused by panel ageing, it is known as maldischarge.

There is a firmware update available for the control board which updates the drive waveforms which can resolve this problem.

The problem is LG did not get the compensation correct for the panel so over time the panel drifts faster than the control board can compensate.

You can try by adjusting Vs down by 10V, and Vsc down by 10V, and Vset-up and Vset-down, to get an acceptable picture, but the only true fix is a firmware update.

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Re: HP PL4260N worth looking at? (photo inside)

Thanks!
Lowering Vsc and Vs did the trick!
I did not adjust Vset-up and Vset-dn though, I was not sure what to look at and the picture looked ok.

p.s. where the firmware update is available? how difficult it is to update?