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Panasonic TX-40DS400E TV red light blinks once, backlight problem

Got a Panasonic TX-40DS400E flatscreen tv with a already damaged LCD screen (torn ribbon cable -> vertical lines on screen) and the 1 blink red light error. Im not really home in tv repairing but I tried my best.

Firstly I checked for any bad components on the boards but found none and then I checked the backlight LEDs, found 2 faulty ones which I soldered out and connected the rest. It was still throwing the same error. After that I tested the measure points on the P-board:

  • SRV24V: 25.8V
  • SRV16V: 16V
  • SRV5.3V: 5.27V
  • SRVLED went up to 51V, but decreased to 25.6V in standby mode

then on the A-board I could only measure the SRV-5.3V for 5.3V constantly, and the SRV-16V for 16V before going into standby mode.

I took a look at the backlight (3 strips) again and saw that the top strip which I took the 2 faulty ones out was turning on for a second, while the other two stayed for longer. (video explains better) But when I connected only the top strip, it stayed on for that duration like the other two.

What can I do at this point?

Update /2024.01.05./ Images of the A and P board, P board schematic diagram

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TNPA6247 1P Schematic Diagram

And I found a service manual similar to this tv, all same boards, don't know if it's usable for this.

Panasonic TX 40DR400 Service Manual

Answer this question I have this problem too

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@doomsday524 looks like you still have some dead LED's on your strip. How are they connect parallel/serial or just serial? If so, then it make sense that they turn off.

Post some pictures of your board and lets see where you measure etc. That way we are all on the same page.

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5 Comments:

Just checked the LEDs on the top strip individually, all works but two are dimmer than the others. Could those be the problem? The LEDs are in series, strips parallel.

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@doomsday524 This looks so much like the strips. Personally, I would replace the top one at least.

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Alright, I'll try that, thank you. It will take a few weeks for it to arrive, so should I leave the question open until then, or click on accept answer?

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@doomsday524 absolutely leave it open until we know for sure things are resolved and properly working :-)

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@oldturkey03 Hey it arrived, replaced the one which had the faulty LEDs and the tv works again. The only problem it has still, the panel, it only shows vibrating colors (https://youtu.be/1cFXtfM8LcA?si=2nuYmxX4...). The ribbon cable is damaged. Could i replace the panel with any 40" one?

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Doomsday524 will be eternally grateful.
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