Samsung BN41-02752A Mainboard Repair

[diablodude64]

Hello everyone, I hope thanksgiving was awesome for you all!

I recently acquired a Samsung 8k QLED 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. 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 that 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.

[diablodude64]

I will probably reflow the CPU unless anyone can tell me the error in my ways and report back unless anyone can think of something I am either doing wrong or haven't tried.

Thanks

[diablodude64]

In case anyone was silently lurking and waiting to find out what happened, here is an update.

On Black Friday I bought an IR reflow station for a pretty good deal. I just got around to reflowing the CPU and it appears my short went away and as of now, the tv is fully functional.

[Shumen]

hi. I don't know English well. I want to fix the same board as yours, I have all the necessary equipment, but I have some questions, maybe you have a telegram or email to contact me.

[Shumen]

Does the TV work now? After you re-soldered the processor?
can you DUMP 25q40?

[rosenrot]

I have the same issue. The Tv restarts when the mainboard is connected to power or the background LED driver.

Is this also what you experience?

Could you measure certain pointe for resistance?

[wsewsad]

100% same error and fixed in the same way by reflow, but in my case there was no short circuit on pin 2-3

[Jnetsab]

How did you manage to reflow/reball as I've the same board here with exactly this issue too.