Panasonic TX-P42UT30E, IGBTs on the SN board

[rivetcity]

Hi,

I'm having problems with my plasma Panasonic p42txu32e. The issue started about 12 months ago.

I have a remote controlled main outlet so whenever I turn off the TV set at night, I also switch off the whole power outlet.
It gives me a better feeling to know I don't have 230V on any cables, so my dog can't get hurt if he gets the idea to start chewing on something.

About 12 months ago the TV started to have the following problem: when pressing anything on the RC to get it on, the red led would go off.

Sometimes it would turn green and keep flashing a few times like it would get on, and then would stop flashing, and the TV won't switch on.
Pressing the ON/OFF switch on the side of the TV set, let it a few seconds off, and then switching ON again, helped. The LED started to flash green immediately and the TV would turn on without pressing anything on the RC.

Sometimes (1 out of 4 times) the LED would flash red, 14 times. So I kept using the main Switch and eventually it would start.

This happened only after letting the TV in standby a few hours. It never happened after switching the main outlet on, like for instance.. it was OFF the whole night, and in the morning after switching the main outlet on, the LED would stay red, and the TV would start normally when using the remote control.

But if I would watch for an hour, then shut it off and let it in stand by the whole day (main outlet on) and then try to switch it back on from the RC in the evening, this problem would reappear.

I got used to this and it didn't bother me after a while.

A week ago, I was playing on my PS4 (for more than 2 hours) and the TV went off. I couldn't get it to turn on anymore. The LED would either flash red 14 times, or flash green for a few times and then freeze. I heard the first relay switching (immediately after pressing the SW on the lateral side) and a second popping (as if the relay would switch off) as soon as the green led would freeze (2 seconds)..

I got the TV opened with no schematic, hoping to see some bad capacitor or a blown fuse. I started to diagnose "in the dark" , I measured the connector of the left side of the power source board (going to the tuner board). The 15volt would be there for a second or two till the relay would switch off.

I removed all the dust, inspected carefully but didn't find any blown part, or signs of thermal damage.
Then I measured the continuity on the PS board connectors. I discovered a short on the connector going to the SN board. Disconnected the cable, and the short disappeared. So the SN board had a short somewhere.
I first thought the big caps right after the power connector were damaged. Then I googled for the MOSFETs (I thought so first) 30f131 and found this forum. I read a post about these IGBTs problem so I started removing them and the short disappeared.
All 4 IGBTs marked 30F131 were de-soldered. Two of them were internally shorted.

I started to look for new IGBTs to replace them. Learned about the "smaller" FGD4536 which would also fit.
I finally found a source near me and bought 4x GT-30F131. The markings are a little bit different and the pins and the thermal pad on the back were a little bit oxidized (not shiny anymore). I had to trim the pins about 1mm cause they were a little bit longer than the original and I soldered them.

I cleaned everything before and after. I cleaned the mounting holes for the screws and looked for discoloration, but found none. In the post I read someone spoke about bad GND connection between the board and the chassis as the cause of the IGBTs failure. So I reconstructed the outer perimeter of the holes by adding tin. Cleaned all the flux residue, put the display's ribbon cables back and mounted everything back on. I switched it ON without the antenna cable, looking at the front LED and hearing for the relay's sounds. The LED came on RED (no more flashing) and as soon as I used the RC (pressed the red button), it started flashing green (but it felt healthy) heard the first relay popping sound and then I got both sound and picture on the display. Problem solved !! Mounted the case back on, brought the antenna cable and everything was peachy again.
The problem was completely solved. The LED would stay RED in standby and the TV would start without issues every time, even after an hour or so in standby.

3 Days after that, the problem reappeared

I still manage to turn it on, but like before the front LED would either flash red 14 times or start flashing green and freeze. 1 out of 7 or 8 times it would finally start, after keeping switching ON/OFF from the main switch on the TV's side.

I didn't get it opened again but I'm almost sure those transistors are failing again.

I need help with this. Can anyone please tell me what is the cause for this ?


1. are those 30F131 I bought (probably not original) failing cause they're bad ?


2. is the main cause somewhere else on the SN board ? I measured all the other power transistors (different markings) and they're not shorted.


3. should I run a thick insulated wire from the chassis to the SN board to make sure I have a solid GND ?


4. does anyone have a schematic for this TV model ?


5. I noticed those IGBT's are in parallel, pairs of 2. But there's also an empty footprint for a third IGBT next to each pair. Would it be wise to try and solder six of them instead of four ? Would it help with the power dissipation ? I know I will also need the gate resistor too. I measured it and it's 8 Ohm ?! I think it's a 1206 package and I'm not sure about the power rating.


6. Any idea where can I find good/ original 30F131 or the smaller equivalent FGD 4536 ? Digikey, Mouser, and all the other suppliers I've tried don't have these parts. There has to be another equivalent part.



Sorry for the lengthy post. Hopefully there's someone out there more experienced than me who can help me. Thanks so much.

[rivetcity]

Re: Panasonic p42txu32e, IGBTs on the SN board

I mistyped the model number. The Correct one is: TX-P42UT30E.

If a moderator sees this, please correct the model number in the title of this thread. Thanks.

[dick_barton]

Re: Panasonic p42txu32e, IGBTs on the SN board

There have been several posts regarding 30F131 fakes and suggestions on readily available replacements.
Did you check the driver IC's and resistors that connected to the mosfets since they often need to be replaced along with the blown mosfets.


https://www.eserviceinfo.com/downloa...ut30e%20j.html

[rivetcity]

Re: Panasonic TX-P42UT30E, IGBTs on the SN board

Thanks for your advice and the service manual. It's kinda fuzzy when I zoom in, especially on the schematics and pcb layout. I did a search after "30F131" and found nothing in the service manual. So basically there are equivalent parts used instead. That's kinda strange... I would expect that from a CN brand.

Anyway, I'll look on the schematic when I'll have some time, and try to identify those IGBT's, their gate resistors and the driver IC(s).

The TV it's unusable again, since yesterday. And I'm under a lot of pressure, cause my gf doesn't want to wait 3-4 weeks to get some new parts from HK or mainland China.. and besides I can't guarantee those new parts will solve the problem (for more than 2 days)

On my checklist this time:

- find *GOOD/Original* replacements for the 30F131 IGBTs. Either same parts or equivalent. Something that won't take longer than 1 week to ship to Germany

- find replacements for the gate resistors. I didn't change them first time. I will this time.

- identify the driver for those IGBTs and source them as well.

- improve the GND - Chassis connection by adding washers or running some thick wires from the chassis to the SN board's GND plane

- add cooling for those IGBTs. Passive (have to look for a way to fasten a small heat sink on top of those transistors). Active (add a small fan)

I'm still in the dark with some of the things here, see my first post's questions. And it still feels like a long shot.

[Biruslapio]

Re: Panasonic TX-P42UT30E, IGBTs on the SN board

This blog contains good information about repairing similar SN panasonic boards:

https://alpengeist-tvrepair.blogspot...d-7-blink.html

It's another model but the fault is the same, shorted IGBTs and screws doing the all the grounding by themselves, maybe you have another partially failed diode or IGBT gate driver.

If you isolate SN and SS boards from the rest of the TV does it power up normally and work even after a long standby period? All Panasonic plasmas that I've repaired can do that.

In the service manual all components of the diagrams have a prefix number to them, for example in SN board, Q402, in the schematics it would be listed as Q16402, then you scroll down to the actual component listing at the end of the manual, it will be labeled there, but Panasonic does not use the actual model number, just an internal code of theirs.

[rivetcity]

Re: Panasonic TX-P42UT30E, IGBTs on the SN board

This blog contains good information about repairing similar SN panasonic boards:

https://alpengeist-tvrepair.blogspot...d-7-blink.html

It's another model but the fault is the same, shorted IGBTs and screws doing the all the grounding by themselves, maybe you have another partially failed diode or IGBT gate driver.

If you isolate SN and SS boards from the rest of the TV does it power up normally and work even after a long standby period? All Panasonic plasmas that I've repaired can do that.

In the service manual all components of the diagrams have a prefix number to them, for example in SN board, Q402, in the schematics it would be listed as Q16402, then you scroll down to the actual component listing at the end of the manual, it will be labeled there, but Panasonic does not use the actual model number, just an internal code of theirs.

thank you so much for taking time to address my questions. I've read that blog entry, I didn't get too into detail.. just read between the lines cause I don\t have so much time now and I still miss the parts to begin the second repairing session.

I have this idea don't know if it's practical. I believe the chassis metal sheet is coated steel. So I could scrape the coating in a place near the board, solder a thick insulated wire that will handle the high current, solder a washer on the other end and then fasten the washer with one of the screws which are holding the SN board in place. Is there any problem with this option ?





If you isolate SN and SS boards from the rest of the TV does it power up normally and work even after a long standby period?


I did try to power on with the SN board disconnected, after replacing the IGBTs the first time. The ribon cable and the 2 wire cable (coming from the PS) were disconnected, only the ribbon cables from the display (the ones on the left side of the board) were connected. The result was 7 or 8 red blinks.
Before I had 14 red blinks. After connecting both the ribbon cable and the ps, the TV worked normal... Only for two days..

[Biruslapio]

Re: Panasonic TX-P42UT30E, IGBTs on the SN board

About the grounding, just use a new screw with washers that's not too long, apply a flat and thin layer or solder on both top and bottom side of SN board ground pads for that screw, and clean the grounding contact on the tv itself, that's it.

I'm doubting these 14 blinks being related to the SN, because waking from standby is all about the PSU and main board, only if the SN board is causing a current surge that is shutting down the PSU exclusively from standby.

To power up the tv with only main board and PSU, disconnect ribbon cables going to SN and the bottom C boards from the main board. It should have a solid green LED, no red blinks.