Question PC shuts down after cold boot, but only sometimes ?


Aug 8, 2009
Hi everyone - I'm hoping to get some guidance on what to do regarding a (faulty?) new PSU that I just installed in my PC. First of all, my specs:

Windows 11
B550i Aorus Pro AX
Ryzen 5900x
G. SKILL Ripjaws V Series (2 x 32GB) DDR4 3600 (running under xmp profile)
Radeon 6800xt reference
Sabrent 2TB Rocket 4 Plus
PSU (see just below)

All of this is inside of an NZXT H1 (v1) mini tower. The NZXT H1 v1 includes a 650w small-form-factor PSU. There are two versions of the NZXT H1, v1 and v2. The v2 had a big sale recently (half off), so I purchased it with the intent to take out the PSU (which is now 750w) and put it into my v1 h1. This I did, and unfortunately the PC became unstable. The symptoms are as follows:

On booting from shutdown, or from sleep, the PC will sometimes shut off after about a minute or two (no bluescreen, just immediately off). It will begin lagging/stuttering just before the shutdown. If I then turn the PC back on, it will usually not happen again. I can proceed to game for hours, sucking up 450ish watts of power, and no problem. But the next day, when I turn the PC back on, it will happen again. The crash always happens about a minute or two after booting up. I will have a Critical Kernel Error 41 (unexpected shutdown) after each.

Okay, so, sounds like a bad PSU to me. So I RMA'd the PSU. In the meantime, I put back the original 650w PSU and all is back to normal, no problems. When I received the replacement 750w PSU and swap it in (new cables, I'm not reusing the old cables), lo and behold, I have the exact same problem again. At this point, I don't know what to try next, so my key question here is:

Do you think I just got unlucky, and got a bad PSU again, with exactly the same symptoms? Or, is there some other interaction between new PSU and my system that might cause this? On the one hand, it seems to me that I've completely isolated the problematic component (PSU) in a controlled way, so the PSU must be the problem. But on the other hand, it seems so unlikely that the replacement PSU would have the exact same problem in the exact same way. Or maybe, that isn't unlikely at all - anyone care to share their two cents?

I haven't simply returned the PSU and get a better brand instead because that means I have to return the entire NZXT H1 case, including the included low profile CPU cooler and GPU riser cable which I do want to keep. That's why I'm trying to exhaust my research here first. Thank you very much for any ideas or suggestions.