Panasonic P42G20E - no picture/sound

[Marco90]

Hello everybody,

I have a problem with my P42G20E.
When I turn on the tv the red light goes on and the two relais on the P-board give a click (one gives a fast click the other stays on). After about 10 seconds the relay turns off and the other one will give a quick click followed by the second one which stays on again. This keeps repeating.

If I push the on button on the remote before the tv clicked again the led will turn green, however when I wait for the relais to click again the light will not turn green.

I found a service manual and checked the voltage on the P-board. I found a voltage of 0.5v on the P15v, 0.33v on the Vsus and 0v on the Vda. All the pins which should have 5v also have 5v when I measure them, and there is also a F15v which has 15.6v on it.

The resistance of the P15v on the P-board is around 3.2k, of the Vsus is around 250k and the resistance of the Vda on the P-board is also around 250k.

This is what I've found so far. Can someone help me find the problem?

[Marco90]

Re: Panasonic P42G20E - no picture/sound

Does anyone have an idea on why the voltage output is so low?

[tw2005]

Re: Panasonic P42G20E - no picture/sound

so no error blink? does the led blink red when this shutsdown?

[Moreno83]

Re: Panasonic P42G20E - no picture/sound

After the second click ( protection ) count the red blinks. ( 7/10 times? )

[Marco90]

Re: Panasonic P42G20E - no picture/sound

There is no error code error code showing.
Just a solid red light.
But when I press power on the remote before the relais start to click again it turns green. If I wait after the click it won't turn green.

[tw2005]

Re: Panasonic P42G20E - no picture/sound

There is no error code error code showing.
Just a solid red light.
But when I press power on the remote before the relais start to click again it turns green. If I wait after the click it won't turn green.

I'm quite confused as to what you describe so I really don't know where to start.

There's two things I'm thinking to try.

One is down the shorted Sc board path, the other is a bad A-board. Take your pick which to try.

option one

turn it off, disconnect these. SC2, SS11, P35, 3 white ribbons at the A board.
now try to turn it on and watch the front led.

See if it completes a startup and locks on solid green, if so grab your meter and check at the P board Vsus ( about 200v or so) P2 or p11 will do, you could also check the other voltages too at the P board but run it long enough to check the turn it off otherwise it will eventualy do a SOS4 blink .

If it just does the same as before then The A board is most likely at fault.

Do NOT reconnect SC2, SS11 and very important P35 until voltages have dropped off or leave it 5-10mins,

If voltage is still at any of those there will be arcing and P35 will potentially damage the panel which will be gameover.

Option two

Disconnect SC2, Sc20 and power on and see if it now produces a blink code

250 kohms across SC2 could be wrong, what is the meter set to? try that again probe it, then disconnect the probe then probe again straightaway and see if it goes over 2 megohms. I forget now what it gets too.

[tw2005]

Re: Panasonic P42G20E - no picture/sound

There is no error code error code showing.
Just a solid red light.
But when I press power on the remote before the relais start to click again it turns green. If I wait after the click it won't turn green.

just some comments here in case this clarifies anything.

when these are first plugged in and the power button on the side is on, the 2 relay clicks will be heard.
If you hit the remote after these clicks, there are no more clicks and the LED should blink green to indicate starting up.
If after turning it on , relays click and the Tv is not activated within 15 secs, they will click again and be in standby. next time you hit the remote you'll hear the relay clicks.

If the Tv shuts down unexpectantly whilst on, eg power failure usualy by default the settings are to return the TV to the last state which will be on, even in a SOS shutdown as far as I know if you turn the master switch off and cycle it the TV will commece startup without the remote.

If the TV has failed and you try to use the remote it will not turn on, will need a powercycle to reset.

hard to know at this point what exactly is happening with yours but should be able to work through it by isolation.

[Marco90]

Re: Panasonic P42G20E - no picture/sound

I've disconnected sc2, sc11, p35 and the 3 ribbons on de A board and everything is still the same. The relais keep on clicking with an interval of aroind 15 seconds. Still no error code showing up.

All voltages, p15 vsus and vda are 0.

[tw2005]

Re: Panasonic P42G20E - no picture/sound

I've disconnected sc2, sc11, p35 and the 3 ribbons on de A board and everything is still the same. The relais keep on clicking with an interval of aroind 15 seconds. Still no error code showing up.

All voltages, p15 vsus and vda are 0.

It's sounding like a failed A-board then as you won't see those unless the A-board commands them to be on. You said you had 5v standby and the standby F15v so my money is on A-board.

SC failure is very common in these so you could check Q661 for short on the Sc board just in case you're really unlucky and have 2 faults but normally doing what you did the TV will turn on or the A-board would, the front LED would lock on green and all voltages present.

Can be real handy sometimes because when the Sc shorts the P board you can get some weird codes. I've read of one instance where shorted Sc caused a 1 blink which is normally A-board and I suggested the above and incredibly 1 blink cleared and was SC dead short .
That was a rare one, I did not expect that but strange things happen.

[tw2005]

Re: Panasonic P42G20E - no picture/sound

Actually just in case, disconnect the lead that runs from the front LED/ IR Receiver board I think they call it K board at the A board and see if it does it still. you won't be able to use remote, if it does not start itself with the master switch then just push the side buttons I think channel up/down can wake these up from standby.

you won't have any led to see

probably a waste of time but give it a go and if you can't tell if it's on or not just set a meter on vsus because if everything passes that'll come up

[Marco90]

Re: Panasonic P42G20E - no picture/sound

Still the same with the K-board disconnected.

So most likely the A-board is defective. Are there parts on the A-board that I could check and replace? Or do you recommend finding a new part.

[tw2005]

Re: Panasonic P42G20E - no picture/sound

Still the same with the K-board disconnected.

So most likely the A-board is defective. Are there parts on the A-board that I could check and replace? Or do you recommend finding a new part.

find a board. could be anything and they do run hot so could even be the main chip on that board . could try warming it up and see if it comes back but not a lot to do unless you have a BGA reflow station, not something I'm into just make sure you check what revision board you have as they differ for each panel size

[Moreno83]

Re: Panasonic P42G20E - no picture/sound

Whats the model nr of the A board?