Bc 250 turn off after 20sec

[Magellan837]

Hello, I have an issue with my AMD BC250. When I first received it, everything worked fine-I was able to install an OS on the hard drive and use it. However, after removing the heatsink fins, changing the thermal paste, and replacing the thermal pads (only on the front side, as I didn't have enough for the back), it now shuts down after 20 seconds of being powered on. This time decreases if I turn it back on immediately.

The thermal paste I used is Cooler Master V1 IC Value, which has worked perfectly for my other PCs. The thermal pad is a no-name 2mm pad I bought on AliExpress, but it had many positive reviews.

If anyone has an idea of what might be causing this issue, I'd appreciate the help. Thanks!

[tayfuryldz]

The fact that it lasts even less time on an immediate second boot makes thermal protection the first thing I'd suspect. Since this started exactly after the heatsink/pad work, I'd stop power-cycling it and re-check contact before looking at software.

The docs call for 2 mm pads on the underside GDDR6, but also say to verify the actual gap on your board. They also call out even heatsink pressure. A pad that's too thick can hold the heatsink slightly off the APU; too thin can leave a component without contact. Missing the rear pads/airflow is another thing I'd fix before testing again.

I'd pull it apart once, look for an even paste imprint on the APU, verify no pad is stacked/misaligned, restore the rear pads, then boot only long enough to watch temperatures. If the paste imprint is poor, that would fit the 20-second shutdown very well.

[elektricM]

@tayfuryldz has this right, and the detail that it gets shorter when you switch it straight back on is the giveaway: the chip is still hot from the last attempt, so it reaches the trip point sooner. That's the APU protecting itself, and after a heatsink job the usual reason is that the heatsink isn't sitting on the die any more.

The first thing I'd look at is the pads you put on the front. You used 2 mm pads under the heatsink. The docs give 2 mm for the memory on the underside, and even there they say to check the gap first. On the heatsink side the pads may need to be thinner: someone on the Discord says 1.5 mm on top and 2 mm underneath. That's one person's figure, not something I've measured, so measure what you took off rather than trusting either number. If the new pads are thicker, they hold the heatsink up and the paste never touches the die.

When you take it apart again:

• Look at the paste on the die and on the heatsink. A full, even imprint means contact; a thin or partial one means something is holding it up.
• Check whether there was grey putty on some of the small parts under the heatsink as well as pads, and that it's still there and not doubled up.
• Tighten the four screws evenly, a little at a time in an X pattern, without cranking them down.
• If you pulled fins out, make sure there are no aluminium bits left on the board.

Let it cool completely between tries and keep each test short.

The missing pads on the back are worth fixing before you use it for real, but they won't turn it off after 20 seconds. Memory without pads gives trouble after long sessions under load, not at power-on.

So I don't send you after the wrong thing, can you tell me:

1. What exactly did you do to the fins? Pull some out to fit a fan (the fin removal on the cooling page), or just take the heatsink off to repaste?
2. What fan is on it, what powers it, and does it spin during those 20 seconds?
3. Is the 20 seconds counted from pressing power? Do you get a picture, and does it also switch off if you just sit in the BIOS setup screen?
4. When it goes off, does everything stop at once (fans included), or does it restart by itself?
5. What PSU is it, and how is the 8-pin wired (the PSU's own PCIe cable or an adapter)? Did anything change there when you did the cooling work?
6. Which BIOS is on it (stock, P3.00, P5.00, a modded one), and did you change any BIOS or governor settings at the same time?

If it still switches off with the heatsink seated properly and the fan running, we'll look at power next. My bet is the pads, though.

This case wasn't really covered in the docs, so I've expanded the Overheating Auto-Shutoff entry and linked it from the boot flowchart.