Z620 randomly turns off, indicates (false?) thermal shutdown

[mpx]

Dear Community!

I have a Z620 with 48GB of RAM, 2x E5-2620 v2 and a Geforce GTX 970 with 3 screens connected to it. OS is Windows 10 x64. Also there's a PCIe NVME adaptor, a disk drive and a SATA SSD. I bought the computer used about a year ago and ever since I got it and stuck the GPU, the RAM and the PCIe NVME adaptor in I haven't made any hardware changes.

What happens recently is that, while doing almost nothing (staring at PDF files or reading something on the internet) the computer just shuts down. The beep code and the flashing of the power button indicate a thermal shutdown according to this page.

When I boot it back up, there's no message or anything, it just boots straight up and I can use it again for a couple of hours until it happens again. I've been watching CPU, GPU and ambient temperatures, though they're around 40 and ambient is around 21 (which is my room temperature, so it seems fine). Also I can't find any kind of log file in the BIOS telling me what exactly was the cause of this shutdown.

I cleaned the computer using a vacuum cleaner, but already before it wasn't particularly dusty, now it's completely clean. When touching the heatsinks I experience the same temperatures the HP Performance Advisor is showing me.

I have tried provoking it by using all the CPUs and the GPU at 100% for a while, the temperatures though stayed in a normal range (GPU was at around 65-70, CPUs didn't really go past 50), therefore I don't know how to recreate this problem, and it doesn't seem like there's a problem with the heatsinks, the heat being transmitted to them or the fans.

Once, after having one of the "thermal shutdowns", I wanted to boot it up, and instead of booting all the fans went to full speed. No output, no beep. This just happened once.

I've read various threads about things like this, but unfortunately haven't found one where someone has exactly this problem. My apologies if it exists and I just didn't find it.

Thank you for any ideas about what could possibly cause the issue!

Merry Christmas!

mpx

[DGroves]

windows logs shutdowns/crashes in several different logging files, please look at them for clues as it may actually be a software program that is the cause

https://www.digitalmastersmag.com/magazine/tip-of-the-day-how-to-find-crash-logs-on-windows-10/

[mpx]

Windows only documented not being shut down. No errors.

In the meantime I seem to have found the cause: I took out the riser and tried without for a couple of hours, the problem didn't occur again. Then I started looking at the risers contacts and I saw that some of the power connector contacts looked a bit "fishy", as if they had melted a tiny bit. (A quick search on the internet revealed that I may not be the only one seeing this)

I cleaned the contacts with compressed air and ever since then it didn't happen again.

I hope I can help other people having a similar issue.