Random crashes/shutdowns

Random crashes/restarts

I'm creating a new thread since there has been no response in the other for a week and I'm unsure if the thread has just been lost in the mix.

The shutdowns are happening while I'm working on the computer. The lights plugged into the wall nearby flicker and the monitor cuts off, and the fans in the computer waver and run at half speed for a few seconds, like power is reduced or there's some kind of power interruption, even though it's plugged into a UPS which doesn't trip. Then the computer shuts down. I'm unable to turn it back on without unplugging or turning off the power supply. This is the core issue. I recently tried replacing the RAM, but the new ones were DOA and I don't really want to deal with buying more right now. I don't suspect the RAM anyway because a RAM check gives no errors and says it's in good condition.

Could it be the power supply? Am I just going to have to keep throwing parts at it like a shitty old car?

It wouldn't hurt trying other lights just in case they're actually causing the mains problems (*). How's the flicker? I once had a very visible one due to a mains issue, the room's light went off for a split second and both the desktop computer and monitor noticed it. But nothing tripped and everything returned to normal, all in a second or less. The computer was quite new and quite well rated in quality. But these issues aren't common at all here, I only recall this one of this class in decades.

(*) I think a combination of a lightbulb with problems and mains devices not too good could cause it. Modern LED lights are probably complicated enough inside, unlike traditional ones, but I have one of the latter that flickers a lot (continuously) if you screw it in too much.

Unplug and remove the UPS .
Then unplug and remove peripherals excepting monitor, mouse and keyboard.
Does the problem still exist ?

Thank you for the responses. I do use a UPS. I first suspected it was the UPS that was causing the issue but I ruled that out by plugging the computer into a nearby socket. If it is a mains issue, wouldn't the UPS alleviate that? But as I mentioned, it's not being tripped/activated by a power interruption when the computer shuts down. And I'm pretty sure it works because it has saved me during actual power outages during storms, at least several months ago [just confirmed it works]. I've also tried plugging the computer into another outlet and it didn't help. But maybe the house wiring is bad. I have had mice in the walls around this room and elsewhere. So I guess I might have to call an electrician and have the wiring inspected.

But before I do that, there is a lamp with an LED bulb that's been flicking for a while that's also plugged into the UPS on the non-battery side. It just hasn't flickered often enough to bother me. So that bulb could be causing this issue, is that right? I'll replace the bulb then.

Have your wiring checked and also your House and Contents Insurance policy for fire clause inclusions.

I think mice couldn't cause this kind of issues, unless (if at all) they gnaw mains devices (differential, power control switch and such). We say here that a cable "falses" or "does false" when its connection isn't reliable, it's absent or intermittent (but not like a car's intermittent or anything flickering, at 4pm it connects, minutes or hours later doesn't, next day or week it connects again...). Normally this could happen inside electric or electronic devices, whose inners can be extremely cheap (some of these cables have one or two aluminum thin threads, obviously not for transporting MW). I've seen it once in mains cables: I had adquired the flat recently, a socket wasn't working (no "flickers", no "issues", just no electricity at all or at least not in both poles), it was well connected and I called an electricist, who replaced an inner section of cable.

Although I'm not specialist in this, I'd say "cables falsing" could happen "chemically" in all cables that aren't too thick and "physically" in thin cables. From mouse gnawed cables I'd expect either just no connection or short circuits. I wouldn't expect "flickers". A damaged cable doesn't have the capacity of lowering the voltage (let alone in "flicker" mode) or limiting the amperage, if it's gone too thin it could either act as a fuse or heat up a lot but still conduct.

My main suspect now is the PSU, and possibly the "110/125/220 V choice" has to do. 110V (US for instance) and 220V (Europe and more) are current standards in different countries or regions, and 125 V was a decades ago standard that lived together with 220 V specially in some rural zones (125/220V transformers were typical in hw shops here). Decades ago PSUs here came with a switch to use them at either 110 or 220V, but from a lot ago such switch is absent, the PSU is made or set at factory for only one of the voltages. Imo it's not impossible that a PSU can work with other voltage for some time, with flaws, and/or not safely.

Ok I've installed a new PSU. By the way, I did upgrade graphics cards to a GTX 2060 kinda just before this started happening and I thought the 550W PSU I had would be enough based on my math. But in case it wasn't I went with a 750W just to give it some headroom. So we'll see if that fixes it.