Panasonic TX-P42ST30 with exploding diodes....

[Moreno83]

Hey guys ,

Im having some big troubles with a TNPA5330 AB board. It's a tv from a customer.

It had the usual 7 blinks and the buffers are all ok! Replaced the 6 shorted fets , turned on the tv and i now got 6 blinks.
I then replaced the 2 small ic's and i got some loud bangs above the white prong connector.

I think that there are also FAKE FGD4536TM igbt's. I got a few from mouser and a few from china.
The ones from mouser got a cut on both corners showing the copper , the ones from china dont have that.....

Anyways to continue the story. The diodes 430 , 432 and 433 were shorted and even popped! Im not sure if this is caused by 1 fake igbt or does the board have a different problem?
Both resistors are bad also!

I replaced the resistors and diodes + shorted fets 3 times now and again the diodes explode.
I even replaced the 4536TM for original rjp30h2a and still the diodes blow. The fets in the bank measure 90ohm after the bang....

Also , when i measure the resistor on the good board it measures 45k. When i put the good resistor on the bad board it goes to 35K...so something is pulling the resistance down.

Something in the energy recovery circuit is blowing up my board.... i got to watch out now as the traces are getting black/broken because of the bangs.

Any idea's what is causing this?

I got a board with a shorted buffer so i can replace parts.....

Ps , repaired the same model for different customer and that went fine!!

Thanks!

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Photo with the diodes that are still fine is from the board with the bad buffers.

Other photo's are from the blown board.

[Alastair E]

Re: Panasonic TX-P42ST30 with exploding diodes....

Did you replace both the transistor driver pairs as well as the little buffer chips that drive each set of IGBT's?
--They ALL should be changed in one hit or there'll be probable troubles...

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

I first got 6 blinks. I then replaced IC502 and Q531 and the diodes on top exploded.

The fets q421/422/423 were shorted again. Replaced them with original panasonic parts. Replaced all diodes and resistors + blue ceramic caps and again all popped.

Did not replace other driver ic's besides IC502.

[Alastair E]

Re: Panasonic TX-P42ST30 with exploding diodes....

Aye--But IF you didnt replace ALL these parts At The Same Time--One will kill another....

What IGBT's were faulty when you FIRST had the set?

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Well yes but not in this case.

The standard 6 IGBT's were shorted. Q421 , 422 , 423 and the 3 above the big capacitors next to the RF1510 diode.

I did not get a bang after replacing the fets , i got 6 blinks. This is a standard situation as i also had it on the repair i did AFTER this board. Replaced the 2 parts and the bangs came...

I left the board as is and started with the other tv. Same board same tv and same parts and this board turned on! Only difference with this board is that i rechecked all IGBT's before i soldered them on , again i took the FGD4536TM from mouser. ( They don't work on the other bad board ).

Im hoping Flocko or TW2005 have seen this fault before or know whats causing this but my personal feeling is that i need to replace almost ALL parts in that circuit.

Possible solution:

Replace all parts in picture 2 + diodes 430 , 432 and 433 + resistors?

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Found a defective board for the customer so thats good. Still wondering what is causing the diodes to blow this hard.....

[tw2005]

Re: Panasonic TX-P42ST30 with exploding diodes....

Have you got a copy of the SC/SN fault finding for 2010 -2011 boards? The one that gives the diode check reading of the driver IC pins on the various models?

What's the deal in picture 3 with the RJP30H2 blown apart? I see that and it's not sitting straight possibly not soldered. Is that you removing it and putting it back for a photo? The other 2 look original.

Don't have any ideas except the basics being, remove all the obvious bad shorted parts, check everything else for short, check all driver resistors and if a driver IC has failed check the resistors associated with that and the 5 pin NPN/PNP.

compare the optocoupler readings to the good board.

Stick to the batch of parts that are known good just in case.

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Hi TW2005 ,

Thanks for joining in.

The RJP30H2A thats standing up straight was like that when i first opened the TV. What you see is a IGBT that is cut in half because of the explosion haha. The customer said that some loud pops came out of the TV.

I'll replace every part in that energy recovery circuit , see what happens!

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

So i had another repair , same tv with the same board. Tried it again and after the ysus repair i found out that the power supply ( TNPA5426 ) is bad also!

Common on this TNPA5426 is that the fuse + 2 other parts blow. They were fine on this power supply AND the power supply from this original thread.
I measured Vsus voltage without the Ysus board and measured 230V just on startup. This means that 230V goes to the Ysus board which probably blow the diodes on top.

Normal Vsus voltage on a ST30/GT30/VT30 is 215V.

Need to find out what is causing this. 2 power supplies now!

[flocko]

Re: Panasonic TX-P42ST30 with exploding diodes....

Not sure I understand what you saying. the R6015s (600v 15a) +fuse failing on the power board are a common fault after a big SN board blow up on this model in all sizes.and with no load (SN unplugged)it is to be expected that the VS would go above the correct voltage

[tw2005]

Re: Panasonic TX-P42ST30 with exploding diodes....

So i had another repair , same tv with the same board. Tried it again and after the ysus repair i found out that the power supply ( TNPA5426 ) is bad also!

Common on this TNPA5426 is that the fuse + 2 other parts blow. They were fine on this power supply AND the power supply from this original thread.
I measured Vsus voltage without the Ysus board and measured 230V just on startup. This means that 230V goes to the Ysus board which probably blow the diodes on top.

Normal Vsus voltage on a ST30/GT30/VT30 is 215V.

Need to find out what is causing this. 2 power supplies now!

I would say dead short on P2 from bad SN. I vaporised the P2 track on a 50" with repetitive SC board blow ups when I was stuffing around with the bad 30F131. I'd be surprised if 230V blew anything. All the IGBTs and diodes are rated above that.

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Hmm , i took a good powersupply and turned the tv and it goes to 215v before it shuts down to 7 blinks. ( with sc disconnected ).

Other ps goes to 215v. Will take another look at the sc board.

[Alastair E]

Re: Panasonic TX-P42ST30 with exploding diodes....

Could try a bulb of 150W 240V in series with VSUS supply--It may prevent further carnage and flying silicon...
--Set will run with this if all is well, but with cruddy picture, but does help determine if its gonna work--Or not!

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

thanks for the tip! I got another repair at the moment , this time a 42GT30 but has the same boards. Repaired both boards and turned it on without the sc board connected. Starts with 207V and jumps to 216V before shutting down to 7 blinks. This is how a good powersupply should work.

Connected sc board and this repair works fine to! So advice is to check the Vsus line after repairing the powersupply board.

Im not going to repair this sc board , its too heavily damaged. Vsus line is almost cracked open and not reliable for sale.

[satinser]

Re: Panasonic TX-P42ST30 with exploding diodes....

2 months on and I have exactly the same problem as you had with the same exploding diodes. Did you ever determine the cause?
In my case D430 and D432 both exploded their tops D433 seems to have survived though.

[flocko]

Re: Panasonic TX-P42ST30 with exploding diodes....

This is common for these to blow the SMD diodes D430/D432+D433 when the IGBTs fail the original RF071L4S(marked 83), they can be a little hard to find now, I have always used the fairchild ES1G as a replacement as most of us would have these for Samsung/ LG Sus board repair anyway, but any 1A 400v super fast SMD rectifiers will sub for them

[sienoki]

Re: Panasonic TX-P42ST30 with exploding diodes....

How do you test TNPA5330 board after repair kit fitted to see if still shorted or not..thx

[Moreno83]

Re: Panasonic TX-P42ST30 with exploding diodes....

Hi Santinser and Sienoki ,

I never found out what caused this issue but I'm still suspecting bad IGBT's. ( Fakes ).
I received a lot of TNPA5330 boards with the same issue , blown diodes on the top side of the board.

It's not only the diodes that are bad. All igbt's , diodes , resistors etc all need replacing , all resistors in that area are dead!! Also the D302 under the heatsink is shorted.

You can't test a repaired board without applying power to the board. Just hope it won't blow up. You could measure for shorts on the white prong connector , beep is bad.

I ordered the diodes that Flocko said. Im planning to replace all parts in that area because just replacing the diodes and resistors won't work.

[sienoki]

Re: Panasonic TX-P42ST30 with exploding diodes....

ls that neg to chassis ground n pos to white connector