Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

[tom66]

No blink code on this one. No picture or sound. Dead shorted SN board.

About 8 x IGBTs shorted. Pulled SN & will get brief Vsus and Vda. Then will lock out with a solid green light, despite relay clicking out... odd...

Pulled SN20 (equiv SC20) and will do an 8 blink code... also odd...

Hardly anything inside it!!

[Moreno83]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

I think its normal to give the 8 blink code after pulling SN20? Your disconnecting the board?
There is no blink code at all? Like dead?

A guy emailed me a few weeks back with almost the same model ( P42U30E ).
He said the led turned yellow , clicks and turns off? Same thing with your tv?
He also had the blink code's when disconnecting the boards.

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Yeah, it's a little odd, but I think i've figured it out. With SN20 out the SS board does briefly produce an SS waveform. SN power disconnected too, so I get some Vsus/Vda.

Of course without SC board the ERC does not work - it relies on the other half doing some work too! Because of this, it shuts down with 8 blinks.

I don't like these new Pannys, there's too little inside... It still pulls 255W, so they haven't reduced the power consumption a huge amount, and yet the SN board has been reduced to a pathetic bath of SMD IGBTs... I cannot see these running at acceptable temperature margins. And there are no fans, either! The PZ80s have 4!

My LED doesn't ever turn yellow...
It only ever blinks red with SN20 out. Everything else, it either turns off power LED or locks solid on green.

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Pictures of the anaemic chassis of the U30B (sold for £449 on release), for comparison PZ8BA (similar model - 2 HDMI 1080p entry level set, sold for £599 on release)

[Alastair E]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Orrible innit!

Nowt inside, and Lots go wrong--with what little there IS inside!

Cost-Cutting to the extreme!

Ive sent you a PM about this chassis, feel free to post here if you like....

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Yeah, I'll copy over some of what I said.

I've got 4 x 30F131's dead shorted (SUS UP and DN) and one DG302 dead, for ERC...
Everything else seems ok, so I think I got a fairly easy one.

I'll briefly put in a 30F131 in place of DG302. It should work as a quick test. I'll use Al's trick of a 150W bulb in series with SN Vsus to limit any fault currents and hopefully catch any failures early.

Once all is shown to work, I'll put in a proper DG302.

I've a semiconductor tester, I think I'll pull most of the IGBTs off and test them out of circuit, just to be sure.

Since floating ground IGBTs/FETs are OK, the floating ground drivers should be ok... the SUS UP/DN drivers should be easy enough to test.

[Moreno83]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Hm , hope you get this 1 to work!

[Moreno83]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

So did you fix the tv? I can buy the same tv for a low price…

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

I'm not THAT fast….! I usually take about a week to fix things. Waiting on parts from a fellow forum member...

[Moreno83]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Haha ok ok

[RJARRRPCGP]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

I don't like these new Pannys, there's too little inside... It still pulls 255W, so they haven't reduced the power consumption a huge amount, and yet the SN board has been reduced to a pathetic bath of SMD IGBTs... I cannot see these running at acceptable temperature margins. And there are no fans, either! The PZ80s have 4!

The corner cutting sounds just like CFL-lit LCDs! (I was beginning to wonder if the PSUs of CFL-lit LCDs usually run hot, but, mostly, that's because they're cramped with zero fans)

Sadly, with the CFL-lit LCDs, seems to happen often, at least according to folks at badcaps.net, even when the watts aren't in Trinitron territory!

(Ones with that combo seem to be wet-electrolytic cap cookers) (It looks like LED-lit LCDs are better, when it comes to temps. Seems to just be lukewarm, even with no vents)

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

LED TVs may run the PSUs cooler but the panels run hotter and fail more often, if the panel doesn't go the LEDs will, both of these can be uneconomical to repair as we've seen on here before because the LEDs are unobtanium and the panels can't be fixed by anything but a tab bond machine.

So I prefer a "crappy" plasma versus any LCD because I can probably fix the plasma if it goes wrong...

[Ragga_NZ]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Hey Sorry to post in your thread tom, but was wondering whether someone could help me troubleshoot my panasonic tv. TH-L32C30Z.

The initial problem was the tv would turn itself off (to standby) about 10 minutes after viewing (continuous flashing of red LED, no pattern). Then after a while it would do this after a few seconds after it was turned on.

I used a remote control and lower volume button on the set to do a factory reset. No it turns on, shows the setup page screen goes dark, setup page comes on again and screen goes dark again, setup page comes on again and then goes dark and stays that way (green led stays on). Whilst this is happening I can hear buzzing initially from the square transformer at the top of the p board and just before the screen goes dark a buzzing sound from the top transformer with the two windings. Can't see any bulging or leaking caps. Any ideas????

Thanks very much for you help

Two vids at
https://www.youtube.com/watch?v=L2YKdowUydk
https://www.youtube.com/watch?v=s70p9ft-vX8

[Moreno83]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Buzzing is not good , would wait for any tips before turning the tv on again. And make your own thread otherwise its going to be a huge thread with different faults/symptoms.

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

YES, please keep your questions in a separate thread. I am not a private help service, there are others here too!!!

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

So....

I decided to lift all the shorted IGBTs off, and put it in the set to test the gate drive waveforms. To my surprise, the ERC LED lit up on the SC board, and the set did NOT trip out with any fault code. The SS board also made a gentle humm indicating the panel was being sustained. I looked at the panel and could see very occasional (like one in a thousand pixels) maldischarge sparklies, but no other image. There was no proper positive reset-ramp like there should be, which would probably explain this...

I am guessing that under no load, the ERC circuit is charged up by a few-100s kohm resistance, and this is enough to keep it from tripping out the fault detect. As there is no other way for it to stop it working.

All waveforms appeared good on the gates of the various power devices, so it's stage two, which will involve installing new devices onto the board. Wish me luck.

[tw2005]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

So....

I decided to lift all the shorted IGBTs off, and put it in the set to test the gate drive waveforms. To my surprise, the ERC LED lit up on the SC board, and the set did NOT trip out with any fault code. The SS board also made a gentle humm indicating the panel was being sustained. I looked at the panel and could see very occasional (like one in a thousand pixels) maldischarge sparklies, but no other image. There was no proper positive reset-ramp like there should be, which would probably explain this...

I am guessing that under no load, the ERC circuit is charged up by a few-100s kohm resistance, and this is enough to keep it from tripping out the fault detect. As there is no other way for it to stop it working.

All waveforms appeared good on the gates of the various power devices, so it's stage two, which will involve installing new devices onto the board. Wish me luck.

Ok, no worries - Good Luck

[tom66]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

Knowing the track record with first-time repairs on Panny boards.......... I'll need it

[tw2005]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

You're obviously having fun though, plugging it in nothing fried and waveforms. Sounds promising. Funny how the SOS detects a fault, but does not miss the parts you've pulled

[Alastair E]

Re: Panasonic TX-P42U30B locked out LED (no blink code), SN dead short

And so--Did you Bulb it.....?