Panasonic TCP50S30 failures

[KEhrhardt]

Hi I'm new to the forum.

I have a Panasonic TCP50S30 that has the 7 blink problem.

Previously I had a failure on the SU board and had a driver chip replaced by someone on eBay. SC board was okay and the repaired board worked for around 6 months and then I got the 7 blinks again. When the SU board failed previously, I had a direct short from the panel ribbon cable connectors to chassis ground and I was able to trace it back to the affected driver IC. So I knew which board failed.

This time I have no shorts from the SU nor SD ribbon cable connector pins to GND. The SC board failed (loud pop and IC 784 pin 5 blown off board), I had the SC repaired from the same guy. Plugged in repaired SC board, pow SC board failed again. D642,Q622,Q623,D643,Q661 all shorted, again IC784 cracked by pin5 carbon sprayed around there. The IGBTs are shorted from G-C-E and the diodes are shorted 1-2, 2-3. Okay, don't have time to fix right now. Purchased a 2nd (working) SC board off eBay for a good price.

I run the isolation test using 2nd SC board by disconnecting the SU and SD boards at connectors SC41, SC42 and SC46, unplug SU11 from SD11, removing the 4 VF screws on the driver boards and with the jumper on SC50. The SC board has the green LED on and I hear buzzing going on, so I think this is good. I connect the 2nd SC board with the SU and SD and go for broke, but I get the 7 blinks, at least no smoke with this SC board. So I must have a bad SU or SD board correct?

So my question is how do I diagnose the SU or SD boards if they have no shorts from the ribbon connectors to GND. I don't really want to connect one or the other SU or SD board to the SC and push my luck and try it again, I don't want to run the risk of blowing up the 2nd SC board. Are there any other weak points on these boards I can check for failures?

Checked resistance from SU SD ribbon connector pins (black lead) to VF (red lead). Set to diode check, I get a nominal .778 on all pins.

Checked resistance on all pins SC41 to VF and SC42 to VF, get infinite on 20Kohms range.

Really love the picture on this plasma set when it is working.

Thanks in advance
Kurt

[dj01fad]

Re: Panasonic TCP50S30 failures

Hello,

check for shorts from the ribbon connectors to the VF screws on the buffer boards.

[tw2005]

Re: Panasonic TCP50S30 failures

Hello,

check for shorts from the ribbon connectors to the VF screws on the buffer boards.

Yes i would follow this path but I have a feeling you may have already done this if you're quoting 0.7 readings.

But yes one probe on the Vfg plate on the buffer board and slowly robe each and every pin on the out puts.

also resistance checks on 6,2,1 on the SD42 with respect to Vfg and 2,6,8 on the Su41.

Auto range would be handy and 2 of these read over 5 meg.

if the buffers check out and the SC passes on the bypass then we have a tough one.

[KEhrhardt]

Re: Panasonic TCP50S30 failures

Update on this 7 blinker set. I found a 14 blinker 50S30 on Craigslist for $50. The Craigslist set had a bad SC board (shorted SC2). Swapped the buffer boards out of the Craigslist set into my 7 blinker set that I put a good SC board into and worked in bypass mode. My 7 blinker 50S30 now works! Woohoo.

So the original buffer board set still has an issue. Still no shorts from the connectors to VFG. More work to do.

[KEhrhardt]

Re: Panasonic TCP50S30 failures

Looks like I have fixed the 14 blinker SC board. Replaced 4 blown 30F131's with the FD4536 parts. The diodes showed shorted at first, but once the 30F131's were removed, I checked them again and they were fine. The TO-252 DPAK for the IGBTs is slightly smaller than the DPAK2 but easy to work with. Getting excited now. Now if I can just figure out the SU and SD card problem, it should be another working set. B-)

[tw2005]

Re: Panasonic TCP50S30 failures

Looks like I have fixed the 14 blinker SC board. Replaced 4 blown 30F131's with the FD4536 parts. The diodes showed shorted at first, but once the 30F131's were removed, I checked them again and they were fine. The TO-252 DPAK for the IGBTs is slightly smaller than the DPAK2 but easy to work with. Getting excited now. Now if I can just figure out the SU and SD card problem, it should be another working set. B-)

Should be a simple case of setting the meter to continuity and look for shorted outputs at the ribbon connectors to Vfg or the metal plates the 2 board bolts were.

i'm finding it's SU and the top couple of buffer ICs failed.

If you're really good you can remove them and replace the chips. There are repair services out there but I remove the silcone first, then cut the legs hard against the body, remove the body and continue removing as much silicone, acetone seems to help break it up, then I carefully desolder by hand, clean up, and desolder pads flat, hand solder new chip.

Pads are easily lifted or torn away.

I've had a few near misses now, damaging pads.

[KEhrhardt]

Re: Panasonic TCP50S30 failures

Yeah ran the isolation test with the jumper on SC50 and it is the SU board, SD board is okay. However I have rung out the connectors on that board over and over and cannot find a short to VFG. You are correct that the 2nd chip from the top was replaced by oleg_yj on eBay last yr and the set ran for about 6 months before it failed again. Also checked the resistance on SU41 and it looks good. I'm at a loss. Maybe send it back to oleg for evaluation.

[tw2005]

Re: Panasonic TCP50S30 failures

Yeah ran the isolation test with the jumper on SC50 and it is the SU board, SD board is okay. However I have rung out the connectors on that board over and over and cannot find a short to VFG. You are correct that the 2nd chip from the top was replaced by oleg_yj on eBay last yr and the set ran for about 6 months before it failed again. Also checked the resistance on SU41 and it looks good. I'm at a loss. Maybe send it back to oleg for evaluation.

I don't know , you'd expect shorted output or an unusual resistance to show on either board.

[KEhrhardt]

Re: Panasonic TCP50S30 failures

Update. Now have both TCP50S30's up and running, beautiful pictures. Replaced the SU/SD pair with a set from AliExpress and all is well. Have extra set of boards SC, SD and SU. SD is good, SC and SU need repair. Waiting on parts for the SC board. The SU is failed but does not show any shorts to VFG. Actually all pins from VFG to ribbon cable connectors are .780 nominal with red lead on VFG and black lead on ribbon pins in diode mode. Perhaps one of the surface mount caps on this board is blown, not sure. The AliExpress boards were AB suffix, original boards were AM suffix. Hopefully this info is helpful to someone.