Panasonic TC-P50U50 Powers Off - 8 blinks

[nobbnobb1]

Hello,

I have a Panasonic TC-P50U50 plasma TV which powers on briefly, then powers off and flashes the power light with 8 blinks. This TV is infamous for this, of which the suggestion that the SS board has failed due to loose grounding screws and requires a replacement of the following components on the SS board:

2x DG302 (Q16051)
2x RF2001 (D16041)
2x 5.6 ohm SMD resistor
1x BD8694 IC

I have already gone ahead and replaced these components, as well as cleaning off the ground connections on the SS board as well as the associated mounting points on the metal frame. No luck. The capacitors also do not look like they've failed.

Sometimes it will power on for a few minutes before shutting itself off. I attempted to use an IR thermometer to see if certain components were overheating and did not find any anomalies.

Does anyone have any other suggestions to try? I'm completely out of ideas now.

Thanks!

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Make sure your solder joints are good, none cold etc, recheck the flexible cables, make sure they are in properly, same for connection to mainboard, beware of fake parts from some chinese sellers. Examples of bad solder joints for onlookers who might need: https://www.google.com/search?q=bad+...ih=607&dpr=1.5

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

If no problems there, I guess check out the rest of the components on that board, maybe check that little mlc capacitor next to the IC and the rest of the caps, might want to use lock washers on the retaining/ground screws to keep them from coming loose and shorting things out. Also suggested to change out the ground screws on the boards, the ones they used always come loose with time, mainly because they used a different kind of metal for the screws.

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Thanks! No apparent issues with the solder joints, which I wouldn't expect any since the SS board doesn't get hot.

I guess the very last resort would be to desolder the capacitors to check? Some of them are connected in parallel...not sure if it's ok to check as is? I also don't have the capacitance function on my meter so I would have to get a new one.

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

I would start with the electrolytics, as they are the caps that usually give up first.

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Can try heating the caps with a hairdryer for a couple minutes then try the tv, see if it works if only for a bit, don't wait til it cools down try it while its still hot.

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Can try heating the caps with a hairdryer for a couple minutes then try the tv, see if it works if only for a bit, don't wait til it cools down try it while its still hot.

That's an excellent trick! Just tried it and doesn't seem to make a difference. TV powers on for about 2 mins, then shuts off.

[Biruslapio]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

did you do the same grounding maintenance for the SC board?

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

did you do the same grounding maintenance for the SC board?

Thanks for the suggestion. I just did this to the SC board and it did not result in any improvement.

[Biruslapio]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

try lowering VSUS a bit to see if it's related to power consumption.

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

try lowering VSUS a bit to see if it's related to power consumption.

Per the service manual here, it appears I can only set the VSUS in the service menu. The screen turns off before I can access this, so no luck.

https://www.manualslib.com/manual/13...Tc-P50u50.html

[Biruslapio]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

The PSU has an adjusting trimpot, I've never seen a plasma with hardcoded VSUS with no analog adjustment option.

If it's 200V or so, try lowering to 190, don't go below 180V as it will prove not benefitial to picture quality (it will start to show some purple pixels).

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

The PSU has an adjusting trimpot, I've never seen a plasma with hardcoded VSUS with no analog adjustment option.

If it's 200V or so, try lowering to 190, don't go below 180V as it will prove not benefitial to picture quality (it will start to show some purple pixels).

Thanks for that suggestion! So I measured VSUS to be 214V and cranked the pot counterclockwise as much as possible...could only drop it to about 202V. However, the TV seems to stay on longer now before shutting off so that's some progress.

One interesting thing that I DID notice was that BOTH heatsinks on the SS board get too hot to touch. In comparison, the heatsinks on the SC board do not get that hot. So I'm guessing that narrows down the problem. What could cause these transistors to overheat?

[Biruslapio]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

I suspect it is some bad soldering or some semiconductor reaching the end of its lifetime and leaking at high voltages and temperatures.

Even 60C is too hot for us, but the IGBTs work fine up to 100C case temperature and heatsinks may be at 80C, so "too hot to touch" is not a conclusive statement.

You can try to lower the plasma contrast(it affects max brightness) in the menu and enable C.A.T.S(dims the overall panel based on light sensor in the front, I have put a black tape on that sensor so these TVs can dim to the max) but that won't solve the issue, just circumvent it at best.

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

I think those suggestions seem to be bandaid workarounds. There are two heatsink sets and they are both getting way too hot which is 100% a problem. I did replace the diode/transistor sets with new units, and the fact that both independent heatsink sets are getting too hot would suggest that something else on the SS board is malfunctioning causing too much power to pass through.

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Can try a test, do it in order then report, with tv unplugged from power, unplug SS33 from SS board, plug power cord in turn on tv, does it stay on?

[nobbnobb1]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Can try a test, do it in order then report, with tv unplugged from power, unplug SS33 from SS board, plug power cord in turn on tv, does it stay on?

Just tried that. TV stays on and all SS board heatsinks stay cool. What does that mean?

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Check for continuity
between pins 1 and 2 of connectors
SS52 ~SS57on the SS board. Do not
plug in the TV.

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

If continuity is ok in all the connectors, problem is prolly in the ss board, if thats ok could be panel problem. Where did you get the replacement parts?

[nomoresonys]

Re: Panasonic TC-P50U50 Powers Off - 8 blinks

Check resistance of the parts you replaced, in case there's a bad part or bad solder.