diablodude64
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Jan 2, 2024, 6:57 AM
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Help with Samsung QN82Q800TAFXZA Mainboard Repair
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Hello everyone,
I recently acquired a Samsung 8k QLED (QN82Q800TAFXZA) tv that I am attempting to repair. Currently, when plugged in, it will power on normally (sometimes after it has sat for a while) otherwise, relays on the power board click on and off every 5-10 seconds or so killing VAMP, VDRV, and Standby voltage. With the mainboard disconnected from the power board, I get backlights instantly and all test points for the above mentioned voltages check out according to what the silkscreen says they should be.
I have been probing around on the mainboard and it appears that I have a short somewhere going to the processor as far as I can tell. I have attached a photo of the mainboard with some markings.
At point 1, the single pin shows 0.8v with the top right pin at 3.3v. The resistance to ground from the bottom single pin is 54.7 ohms. Is that normal or is that shorted? This might be an ignorant statement but none of the other IC's with the same part number on them are anywhere close to this. The IC just below point 1 is the same chip and the single pin to ground resistance is 5k ohms as an example.
All of the resistance readings at:
Point 2 and Point 3 are 2.5 ohms.
If I inject voltage at the single pin of Point 1, my thermal camera shows the processor heating up at point 4. A small section within that circle but it's very repeatable as I would think it should be.
I have now spent enough time on this such that I would really like to get to the root of the issue before purchasing a new board. I really enjoy the satisfaction of solving these puzzles but it's also not my expertise. I have been watching video after video on YouTube for help and I have scoured the internet for a schematic but I believe this being a 2020 model is still potentially too new to find a schematic.
I have a second power board that was included with the tv and both yield identical behavior when the tv is plugged in. Cycling relays on and off every couple of seconds. When the relays cycle the standby light also turns on and off for what that's worth.
If anyone could help me with some next steps, I would much appreciate it.
This is posted on another forum as well so I hope this isn't an issue as I don't see an option to attach the photo mentioned above so here is a link with the identical post.
https://www.eevblog.com/...2a-mainboard-repair/
Happy new year all!
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