Panasonic TX-P42GT20E 3D , does not turn on!

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

I will try to measure some components on the A board for shorts.

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Ok i installed the fans and the V20E is now working perfectly inside the GT20E chassis. Now i need to wait for the D board to arrive to test the GT20 mainboard if its short or not.

Can i test the mainboard for voltages?

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

I asked the owner of the TV what was connected and he said the tv was connected via hdmi to a hd receiver. The hd receiver was also toast....
Does this help for fault finding?

[tom66]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

It points to power surge damage... Probably a lot more than that one IC damaged unfortunately...

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Yes indeed. I did what TM2005 said and removed D25 from the D board and the tv does not turn on so im guessing its the A board.

So it could be as easy as a small cap but we will never know....
Nothing i can do except buy a second hand mainboard?

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Meaning the D board works as its turning on the tv.

[tom66]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

There are schematics available, so you could try tracing through signals and supply voltages. Usually if HDMI is affected though you're looking at the main processor being bad... which is often not available except on new boards.

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Thx , replacing the processor is not possible for me....i dont have the equipment to reball/replace.
I'll search for a second hand mainboard and fix the tv. You got 1 laying around for sale?

Btw , the picture is amazing!! To bad the misses wants to keep the philips ambilight :/

[tom66]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Plasma is better. You can buy Ambilight retrofit kits for TVs. I'm building one of my own for my KURO.

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

I agree but my gf is the boss!
Pff cheapest mobo i can find including postal costage is 80 euro :/

[Neelix]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

So the USB section, HDMI section, external HD receiver was toasted by the lightning strike. That already is a sign of the severity of the damage and like tom66 said, other parts are most probably going to be toasted as well and since you don't have the equipment to replace processors, getting another board is probably your best option

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

thx for the replies!

Yes of course , thats whats i thought also but i tried something…. ( Not giving up yet ).
With so much current going through a main board i would say that a lot of components would be bad…right?
As i have the main board from the V20E installed and its running perfectly i thought i measured some voltages on regulators/caps and most of the voltages i measure are 15V / 9V / 5v / 6v / 1v / 1.8v etc ( on different ic's , voltage regulators , small capacitors ).

I then placed the "faulty" main board back into the set with the LVDS cable not connected to the main board. I turn on the TV and i get the following readings , before it clicks again due to the lvds cable not being connected.

IC5290 : 9v / 15v ( same on V20E )

Q5502 : bottom row = 1.5v 1.5v 15v , 15v ( forgot top row… doh! )

Q5500 : 10v , 15v , 6v , 0v, - 1.9v , 8v , 1.3v , 0.7v
Q5303 : 1.8 , 1.2 , 1.2 , 0.7 v ( again did not write down bottom row ).

Q4251 : top row -> 15v , 15v , 1v , 1v
bottom row 1v , 1.3v , 0v , 4.5v
There is a similar ic above Q4251 and reads 5v 6v 6v 0.8v , 0v 0v 0v 0v. ( not in this order ).

There are a lot of small caps on the board that read 15V when i power the tv on.
I don't have a service manual for this tv but maybe someone can tell me if these voltages look ok?

[AFajitas]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Lightberry looks pretty good

https://www.youtube.com/watch?v=My9dNb9qOnA

[tw2005]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

I would read through the training guide and follow the start process and confirm what voltages. and signs there are like relay clicks, red led at the optical jack etc. It may be that the voltages are present but one of those main ICs is fried.

never found Q4251, but 15v in and 9v out at IC5290 is correct and interesting since the F15v is part of the startup voltages needed.

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Thx again for the reply!

Yes i'll look in the manual today for the voltages! And indeed its interesting , it might be that the D board is short? There are absolutely NO voltages when the D board is connected to the A board.
The D board does not have any voltages either , yes some 0.5v.......

[Neelix]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Interesting yes. You can get a service manual for the GT20B from Elektrotanya. Should be same as GT20E



When the D board is plugged in, what voltage you get at pin 5(STB5V) of P25 connector?

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

I will check that when i get home!

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Neelix , with the original mainboard and D board connected i get 5v on pin 5/P25 on the powersupply. Thats good right?

[tw2005]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Have a read of that training manual, eg slide 65

[Moreno83]

Re: Panasonic TX-P42GT20E 3D , does not turn on!

Ok , i just did! Brings me to the A board , TU2901A.

Im sorry , i know what I'm seeing and i understand schematics a bit but i don't know what to measure or test right now.