Panasonic TX-P42GW20 display flickering after some time

[Hollusion]

The TV turns on and works fine. After about five minutes the display starts flickering. Where do I start to look for the source of the problem?

Video of flickering: https://my.mixtape.moe/pjgtmq.mp4
Pictures of boards: https://imgur.com/a/UWhAO

[Alastair E]

Re: Panasonic TX-P42GW20 display flickering after some time

All inputs affected...?

Menus flicker too?

Sound OK?

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

The screen flickering will also occur if no video source is connected. Sound is working fine. Anything else I could test?

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

Video link is dead. Here is another one: https://youtu.be/zx6GWzvlUAQ

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

I was not able to find anybody else who had this problem in the past. So this TV is dead?

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Nah not dead! It looks like a mainboard problem. ( heat ).

Did you open the set?

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

Hey Moreno, thank you for your reply.

The TV is still disassembled and I can see all the boards as show in the imgur album (https://imgur.com/a/UWhAO).
The mainboard is the on in the center? (https://i.imgur.com/Dl6Fpqp.jpg)
I am not able to see any damaged electrical parts on it. I'd like to test or mearue them but I don't know where to start.

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

No problem! It is a good tv , don't throw it away!
No the mainboard produces the picture and it is the board on your right hand side.

On the main picture you see the following boards:

-Upper left you see 2 small buffer boards and the SC (Y-sus ) board.
-Middle board is the power supply
-Small board next to power supply is the tuner board
-Board bottom right is the mainboard with HDMI/CPU/GPU chips.
-Top right board is the SS ( Z-sus ). board.

Because this is a image problem i suspect the mainboard is defective. I suspect the board is generating to much heat which causes the image problem. Bad solder under the GPU chip and when you turn off the tv the solder comes back together and picture is fine......

I can understand german and i think you already did that but try to put the tv back to factory settings......

What happens when you enter the service menu?

Hold the Vol - on the TV itself. ( not remote ) While holding this, press INFO on the remote three times. Continue holding Vol -
It can be a different button on the remote like INFO / MENU etc.

https://www.youtube.com/watch?v=7gosP70-JtI

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Ps , when the problem occurs could you apply some pressure on the heatsink of the mainboard? It is the black heatsink. Use your finger and press on the heatsink and see if it changes the symptoms.

Don't put your hands on all the other boards because of very high voltage! The mainboard/heatsink is relatively save to touch. ( low voltages ).

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

I put the TV back to factory settings and made a screenshot of the service menu afterwards https://i.imgur.com/LyzUYUF.jpg

Pressing the heatsink while the TV is having the display problem did not produce any visible change.

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Ok , does the same problem occur when you leave the tv in service mode?

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

Yes it does. Takes about 1-2 minutes until the problem occurs. I also immediately turned off/on the TV and went straight into service mode to check if it still shows OK for all values. It does, but shortly after the problem occurs again.

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Ok , i am not sure if the service menu info is also coming from the mainboard or from the panel itself.....
I still think the mainboard is the problem but im not 100% sure!

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

I am almost 100% sure because the but the only way to find out is to order a new or used mainboard from ebay or from tvonderdelen.nl

TNPH0838 1A is the part number , you need to look at the white suffix sticker on the right side of the board ( small sticker reads TXN/.... )

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

Is it this one? https://i.imgur.com/H8dUoB8.jpg

Thank you so much for helping me!

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

No problem!
When a panel fails its usually something like a black vertical bar. If one of the other boards fail the tv will blink and wont turn on.

You could try to remove the mainboard from the tv and remove the black heatsink and install the board WITHOUT the heatsink. Maybe the heatsink is pulling on the gpu because of the heat. ( gpu stuck to heatsink and not the board ).

Yes that is the one. All the other boards with different suffix numbers will work also , its more for region. Some boards like in the UK have different tuners and if you use that board the coax might not find any channels. ( dvb-c , dvb-t etc ).
If you use something like a HD receiver then you dont need to worry.

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

The heatsink came off pretty easily. Removing the board from the TV was not neccessary. https://i.imgur.com/JDxmtkV.jpg

But the display problem remained the same. I can also hear a buzzing noise. I think it's coming from the power board. But that should be normal, right?

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Ok , i still think its the mainboard.

The buzzing noise you hear is the panel , it is normal. It will go up and down in sound , it depends on what the tv is displaying.

[Moreno83]

Re: Panasonic TX-P42GW20 display flickering after some time

Ok , while the tv produces the problem. Could you press on the other chips on the left side of the board? They dont have heatsinks. Try to press a little in the area of the white ribbon cables also.

[Hollusion]

Re: Panasonic TX-P42GW20 display flickering after some time

Unfortunately pressing on different parts on the mainboard did not have any effect on the display problem.