Panasonic TC-L26X1 - no power

[Greg K.]

Hello.. I'm trying to diagnose a problem for a friend. Panasonic TC-L26X1, seems to be dead, no lights, relay clicks or anything when plugged in. Last resort is a new power supply board, but I figured I'd try to save her $50. Since there are no relay clicks, I'm guessing something in the standby section of the board is bad.

Fuse is good, caps all look good and I'm measuring 120V past the coils at the bottom, and at the thermistor in the lower left. No power from the bridge rectifier, but it seemed to test ok with the diode tester of my multimeter. Also checked the numerous other diodes and found nothing seemed off. Thoughts on what to trey next?

[tom66]

Re: Panasonic TC-L26X1 - no power

Does the unit have a relay on the power board?

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Two of em.

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Photo of back. (iPad I'm posting from will only let me attach one photo per post as I think it names them all the same)

[Greg K.]

Re: Panasonic TC-L26X1 - no power

So.. should there be any relay clicks when power is applied? I guess the two relays that are feeding the bridge rectifier are triggered when the tv is turned on. PCB has a spot for a third relay but they just have the thermistor there instead.

Guess I need to figure out where to check for the standby power and trace back from there. Found the service manual for the TV but it doesn't have much info on the p-board.

[tom66]

Re: Panasonic TC-L26X1 - no power

Check across here. What voltage do you see? Expecting around 160V.

[Greg K.]

Re: Panasonic TC-L26X1 - no power

163V there, yes.

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Hmm, looks like there's 163V going into the transformer (41-603), nothing coming out.

[tom66]

Re: Panasonic TC-L26X1 - no power

OK, check the voltage across each of the blue ringed capacitors, red probe on positive end black on negative end (marked with white strip.) Number readings from top to bottom as in my diagram.

Also please get part # of the green highlighted device -- this drives the standby transformer.

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Green circled IC is A6252. Pic attached.

Capacitor voltage from top to bottom:

0V
0.5V
10.9V
19.9V
17.0V

[budm]

Re: Panasonic TC-L26X1 - no power

Seems like the STBY power supply is working, check the DC voltage on that cap (C501/601?) just above the transformer (stby xformer with 41-603 label on top).

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Cap C601 = 5.7V. Also found the STB5V pin on the connector to the A-board and it's also reading 5.7V. So what to check next?

[Greg K.]

Re: Panasonic TC-L26X1 - no power

Looking at the service manual, found Standby 5.7, 3.3 and 1.8V on the A-board and they all check out. Somewhere when poking around with my multimeter probe I triggered the power supply relays on and the LED on the front came on. All voltages were present on the A-board connector from the P-board. TV still doesn't do anything....

Guessing that the A-board will need to be replaced. These seem pretty scarce may be more trouble than it's worth.