Panasonic TC-P42S30 - Solid RED LED - No Blink

[signal.quest]

Hello. I am hoping the very smart helpful people of this forum can help me repair my TV. Here is the history of the what I have done so far.

I was given the TV by a friend who was going to throw it away because it did not work.

The TV definitely had a bad TNPA5349 board that was shorted across the power input. I sent it to a repair service on ebay and was told it was rare case and not repairable.

I then bought a refurbished TNPA5349. Before installing it I checked for a shorted power input and it was good. I installed it and powered on the TV. I could hear the relays click. The green LED's are lit on both boards. However, the front LED stays solid RED and I never see a picture on the TV.

I went through the troubleshooting manual in detail and checked the various power supply outputs to be as expected. The manual pointed to a bad A (logic) board. I purchased 2 different A (logic) boards from 2 different sellers. Both sellers informed me they were pulled from TV's with cracked screens. Sadly, both of the logic boards I purchased behave the same way. I still have the solid RED (NO BLINK) LED.

Can anyone help me determine if I have 3 bad logic boards or something else is my issue? How can I determine if the panel is bad? Please help. I would greatly appreciate it.

[dick_barton]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Have you viewed and tested the components shown in the video.
https://www.youtube.com/watch?v=BOVlh1Vajv0

I believe that the circuit boards should all be screwed down securely in place before powering up or the boards can be damaged

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Thanks, but unless I am mistaken that video is for a TV with no LED, my issue is that I have a solid red LED with no blink code. I have also checked the power supply and it seems to be working.

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

I have more details to share. I am hoping it helps solve my issue. I can't see any indication the panel is lighting in a dark room. The power switch on remote and TV turns the TV on and off. From the troubleshooting guides this says that the TV is not locked out, but I don't understand what this means. I just have no display at all. I also plugged in my laptop to the sound input on the RCA jacks, but I could not hear any audio when changing inputs on the remote or TV. I am thinking I should buy a 3rd A board from ebay, but that is crazy. ;-) Please help if possible. Thank you.

[dick_barton]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

One site offering a repair service mentions the following which may be worth checking.

REPAIR SERVICE TNPA5349 (AB) If C842 is short then it's a buffer fault.

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Thanks, I will check. Is it possible to have a buffer fault or short on C842, but still have a green LED on TNPA5349 and no short on SN2?

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

I have not been able to locate C842 on the board. Do you know where I can find it? Thanks.

[tvtimmy]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

To test the buffer ic chips: put your meter in continuity mode, as if checking for a short.
Put one probe on the tpvfg(test point variable floating ground) circled in 1st pic.
Open all ribbon connectors to expose the very fine pins. Take other probe and slowly drag across each ribbon connector, front and back. If you hear a beep,you have a short.
If you don't have a short, test all the fets in DIODE MODE to see if they are still working.
Did you notice if a few of the screws were very loose on the SN board? Black arcing marks around the screw holes?

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

I am using a refurb TNPA5439AB because my original was definitely bad. My replacement seems good, the buffer test you mention passes without shorts. I tested it while mounted in the TV - is that a valid test? The green LED is also ON the board and I have no shorts on SN2. I have not tested the FETs since I have no short on SN2, but I will if you still think it is needed.

I have also tried 3 different A boards with the same result.

I am lost now. Any other advice would be great.

[tvtimmy]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

You may just have missed a connection someplace. I would also check the fets, especially the DG302s.

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

thanks! I did miss a connection. I did not realize that the plasma panel ribbon connections into the TNPA5439 were not in far enough. I checked them and got picture!

However, I had lines across some portions of the screen and was missing the bottom row entirely. I started trying to adjust the ribbon connectors to fix the issues in a trial and error mode. I was not making much progress. After the 10th time I forgot to disconnect the power and I blew out one of the buffer ICs! Damn! I ordered another replacement TNPA5349 board.

[dick_barton]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

You need to make any ribbon adjustments while the set is powered off so that you don't damage the board.

[tvtimmy]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

1000+
Always unplug!!!!

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

I learned a tough lesson. :-(

Can you please offer any advice on adjusting the ribbon cables. It seems I was not getting very far after 10 tries.

How difficult/impossible is it to replace a buffer IC? I read 2 shorts on the one set of ribbon connectors.

I did a quick search but could not find the exact IC for sale.

My IC reads:
Panasonic
AN16520A (This number is easy to find)
116P31HC (I can't find any that match this number - is this critical?)

[tvtimmy]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

They are very hard to replace, I have a hot air rework station, and a digital microscope, and I cannot do it.

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Thanks. Any advice on adjusting the ribbon cables? Does it really take many times to get it right? Any tricks?

[dick_barton]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Theoretically the answer is no. Patience when inserting the ribbons and ensuring that the contacts at the ends of the cables are not damaged by forcing the cable into place. You may have to do it more than once. Also ensure that any latches are lifted before insering the ribbon and closing down the latches again.

[tvtimmy]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

When you only see 1 millimeter of gold under the latch, it should be good. You can loosen the board screws to help get them in, BUT DO NOT TURN ON THE TV WITH THE SCREWS LOOSE, YOU WILL WRECK THE NEW BOARD TOO.

[signal.quest]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

Is there a way I can test or visually inspect the ribbon cables are good before installing the new board?

[dick_barton]

Re: Panasonic TC-P42S30 - Solid RED LED - No Blink

You can check the gold/silver contacts at the ends using a simple magnifier.