Sparkles - Philips 42PF9431D/37

[capkid]

I'm repairing a Philips 42PF9431D/37 plasma which had an audio board problem that caused 7 blinks, and I'm at the point now where I'm making adjustments to the picture. I'm seeing a couple effects onscreen: (1) It appears that pixels aren't being extinguished timely, which creates a trailing effect that's most noticeable on dark backgrounds with motion (e.g. Directv screensaver). I also notice this when I bring up the TV's menu then close it; the menu leaves sparkles that gradually dissipate. (2) The typical problem sparkling that's visible when video is displayed onscreen is less noticeable after I adjusted VSCAN voltage.

What I've done so far:
- All panel voltages have been adjusted to within spec. I gradually adjusted the VSCAN voltage down from -190V to -182.5V, which only had a minor effect - nowhere near acceptable.
- Checked Y-Sus caps' ESR in-circuit - no anomalies noted.
- Checked voltage at the Y-buffer connectors: -76V noted at the top pin of the upper connector (I think that was the pin I checked) and -71V noted at the bottom pin of the lower connector (I think that was the pin I checked). I wasn't sure of the significance of these voltages or their disparities.

Note: Ignore the double image in the Directv screensaver pic (took the pic with my phone) - the trailing sparkles are the issue.

[tom66]

Re: Sparkles - Philips 42PF9431D/37

For sparklies, play around with Yrr/Yfr on Y-main until picture looks better. Just a matter of finding the sweet spot.

[capkid]

Re: Sparkles - Philips 42PF9431D/37

For sparklies, play around with Yrr/Yfr on Y-main until picture looks better. Just a matter of finding the sweet spot.

Yeah, I saw a post of yours in another thread, so I started adjusting them - didn't turn out so good. I'm continuing to play with minor VS, VSCAN, YRR, and YFR adjustment combinations to see if I can get an acceptable picture. So far, it looks bleak . Is there anything to the Y-Sus connector voltage variations I mentioned?

[tom66]

Re: Sparkles - Philips 42PF9431D/37

I'm unsure about those readings. Checked the VSET and VE too?

[capkid]

Re: Sparkles - Philips 42PF9431D/37

I'm unsure about those readings. Checked the VSET and VE too?

VSET and VE match the panel label.

[tom66]

Re: Sparkles - Philips 42PF9431D/37

In which case, I would suggest adjusting them from the panel rating, as they too can affect sparklies.

[capkid]

Re: Sparkles - Philips 42PF9431D/37

In which case, I would suggest adjusting them from the panel rating, as they too can affect sparklies.

Ok, I'll carefully adjust those voltages and see what happens.

[capkid]

Re: Sparkles - Philips 42PF9431D/37

I tried all sorts of combinations of adjustments, but I still get a sparkles that dissipate as the image transitions. Do you think I might have a logic board issue? Adjusting the YFr cleaned things up only slightly. Again, nowhere near satisfactory.

[tom66]

Re: Sparkles - Philips 42PF9431D/37

It's not a logic board issue. It's possible it's related to the same problem LG has/had, as the panel ages new firmware needs to be loaded to fix the problem with the sparkling pixels.

[capkid]

Re: Sparkles - Philips 42PF9431D/37

It's not a logic board issue. It's possible it's related to the same problem LG has/had, as the panel ages new firmware needs to be loaded to fix the problem with the sparkling pixels.

Crap. I forgot to mention that I updated the software via the USB port when I first noticed this issue, but it didn't help. It's just odd that the sparkle effect I'm seeing is sort of a retention issue.

[tom66]

Re: Sparkles - Philips 42PF9431D/37

It's common for the same thing to appear on LG panels too.

[capkid]

Re: Sparkles - Philips 42PF9431D/37

Here's a quick waveform capture from the Y-buffer. I took a shot on a used logic board - may not fix the problem, but it wasn't too expensive. I have the latest firmware ready to load when it arrives.