Panasonic TX-P42GT20E Plasma TV: 13 blinks, A-board failure?

Good morning, everyone.
My Panasonic TX-P42GT20E 3D Plasma TV, which I used for my PS3 in 3D, has stopped working. The screen turns on, but there is no video signal, I mean no display of the current source, audio volume level, or system menu.

The TV receives signals from the remote control (the LED flashes), but nothing happens. It won’t even turn off. I can only turn it on and off using the main power button.
I managed to trigger the diagnostics; the LED flashes 13 times, which indicates a critical error on board A—the board with the main processor. I can provide the service manual if you’d like more details.
Does anyone have experience with this device?
I’d like to remove the board from the TV to take some measurements, but I have no idea how to power it since the connectors are all proprietary and I don’t have an external power supply (which I could buy).
I found a replacement board on eBay, and even though it’s a bit expensive (70 euros), I’m considering buying it. I’d still like to try repairing the damaged board (I’m just an hobbiest), though. The board code should be TNPH0899 or TXN/A1NBUE.
Also, in the attempt to put out the board, I cut the flat cable connected to the Satellite tuner (which I do not use) with my finger. Do you know where I can find a compatible flat cable? Maybe one of these Chinese companies like PCBWay could be able to replicate it?
Any suggestions?
Thanks, everyone
AI: Have you already checked any voltages or done any measurements on the power supply/A-board (for example standby 5 V, Vsus, 15 V, etc.), and did the fault appear suddenly or after some event such as overheating, storm, or previous repair attempt?
no
AI: Can you share the exact part number/revision written on the A-board and, if possible, the markings/part number on the cut flat cable or its connector? That would help people confirm whether the eBay board and a replacement ribbon cable are compatible.
The board code should be TNPH0899 or TXN/A1NBUE
The code on the flat cable is not readable but I can upload a photo

Good morning.

This is an older and more difficult to repair TV, and faults may result from overheating and age.

If this is the Service Manual -> Link A-BOARD = TNPH0899.

The power supply may be the cause of the problem.
Check the condition of the solder joints on the P-Board and the condition of the electrolytic capacitors such as C901, C801 and others.
They may not look like the ones in this thread yet, but their capacitance should be measured and replaced.
It's a lot of work and component costs, but that's where you need to start.
If you have an oscilloscope, you need to check the oscillograms of the supply voltages like.
And everything must be done gently and carefully.
This TV doesn't forgive mistakes, and those mistakes are very costly.

The broken ribbon cable between the A-Board and the XS-Board is part number TSXM026.
See the Service Manual, pages 110 and 115.
It's on eBay for 15 Euro - Condizione: Nuovo.

I'm not sure if the ribbon cable is necessary, but not having it may cause a self-test error.
You may need to check disable the XS-Board. Service Manual page 18.

Hi, thank you for your comment.
First of all, I have to say that I don’t feel comfortable testing high-voltage circuits. I don’t have the necessary skills or experience.
Before reading your comment, I was about to buy a new “A” board because the diagnostic sequence pinpoints the problem on that specific board; I found one on eBay from an Italian seller who lists it as a TXN/A1NBUE board, but from the photos, it’s clearly the TNPH0899 board.
I assume you’re a highly experienced technician, and your approach is to start by checking the voltages and capacitors (given the device’s age) to verify that the A board is properly powered. I’d like to do something similar, but I’d prefer to use an external power supply to avoid the risks associated with high voltages. As I mentioned in my first comment, I wouldn’t know how to power it.
To summarize, you’re advising me not to rely 100% on the self-diagnostics. The problem could be related to the power supply board. Is that correct?

Error codes are very helpful in new equipment where the failure is due to damage to a specific electronic circuit.
In older equipment, an error code may be caused by the malfunction
of many components seemingly unrelated to the reported error.
Therefore, in older equipment, before actual repair, it is necessary to eliminate
any irregularities resulting from aging components and only then perform the repair.

Example:
I've had an LG 42LC2RR for 8 years, which I bought
faulty with a remote control for 50 zł (12-15 euros).
It's an older TV (2006/2007) than yours.
It randomly displayed every possible error, and the problem was
old, overheated components in the power supply.
The replaced capacitors cost about 80 zł (15-18 euros),
more than the TV, but after the replacement, all the problems ended.
I wish it were the same for you.
The recording HDD is damaged, but I don't need this option, just like you, XS-Module.
And you can get used to the randomly appearing message - Disk formatting in progress.

Replacing the power supply module in these older TVs is very difficult.
It requires multiple supply voltages and a high current.
This can also generate other errors and problems with A-Board diagnostics.
Replacing modules is necessary if the damaged components cannot be purchased.
As in this case -> Link - with a different error.

Repairing old electronics, even with well-known faults, is not easy because you have to take into account the device's years of service.
Repairing old electronics, even with well-known faults, isn't easy
because you have to consider the device's longevity.
There's always the risk of replacing components that may not deliver the expected
results. However, it's worth limiting the costs to replacing a dozen or so small components rather than
spending large sums on old modules with unknown history.