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Old 04-26-2022, 11:04 PM   #1
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Join Date: Apr 2022
City & State: La Verkin, Utah
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Default Panasonic TC-P65ST50 plasma in protection mode after incident

Hello everyone! I picked up this 65" ST50 plasma TV for $80 on Facebook marketplace two weeks ago. I have the basic electronic knowledge of a teenage computer geek, having assembled laptops and PCs and messed with soldering and software.

This afternoon I decided to disassemble it to mitigate a buzzing noise. This is a well known issue for this TV ever since they were new. The popular solution is to replace the loose internal screws for ones with lock washers, preventing any future buzzing. I figured that I could just fully loosen and tighten all of the screws securing the sustain boards to make it go away. After doing so and putting on only the wall mount screws to secure the rear panel, I turned the TV on. I was disappointed because the effect of tightening the screws seemed to be minimal compared to beforehand.

In the spur of the moment, I thought I could stick something into the vent grate to stabilize the board and/or feel the vibration coming off. My tool of choice was a metal allen key and I stuck it in and touches one of the hollow metal arches marked on the circuit board for high voltage. Of course, there was a fat spark and a loud bang, and the panel immediately went totally black. I cannot say there was any fault but my own here; my only hope is that I learn a hard lesson not only of proper conduct but also how to fix the mess I've made.

I took it back apart but I couldn't find any visually bad components or tested bad fuses. I figure anyway that a failure that immediate wouldn't blow a fuse or cause a capacitor to fail in a visible way. I put the TV back together to start doing research.

When it's first plugged in, a relay clicks regardless of what else goes on. When the power button is pressed, a relay clicks but then clicks off again after a few seconds. The power light blinks in sets of three repeatedly. I found one source that instructed reset it by unplugging the TV, holding down the power button, and then plugging it in and holding it. When I did that, the relay still clicked when it was plugged in, but the power light and the other relay didn't come on until it was released.

I found this link showing that the 3-blink alert on a concurrent model Panasonic meant a failure of the A-board.
However, every other piece of information I can see seems to point to the power supply board. The hope would be to repair some superficial component, but really I just want to see if this will be worthwhile to fix. Thank you to anyone who read this far and for any information provided. I am grateful for the wealth of information available on this forum.
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