Why does my PC crash only when my cat is nearby? [closed]

I have a cat and he likes to walk around behind my desk, which is where my PC is. Somewhat frequently (at a rate of several times an hour) while he is doing this, the screen will suddenly turn black and after a few seconds, the fans stop spinning and the computer restarts.

At first I thought he might be jostling cables back there in a way that somehow causes a crash, but I haven't been able to reproduce the problem by wiggling cables myself, and once I started trying to diagnose the problem I quickly noticed that it happens even when he hasn't actually touched the case or anything connected to it. He can trigger it just by walking within a few feet of the case.

I have never observed the computer to crash like this when he's not around. I've been keeping track of when he is and isn't in the room and I always keep programs open on the computer so that I'll know if it has restarted (because they will be gone after a restart) even while I'm away. I was doubting myself at first but at this point I am 100% certain that it really is my cat causing this.

I built the computer early in 2020 and this problem first appeared a couple weeks ago. It is the coldest it's been all winter right now and although I run a humidifier in my room, it's not very effective and the air is still dry enough, and my cat's fur is thick enough, that he seems to be able to build up static merely by existing. So I'm guessing it likely has something to do with static electricity, but I don't understand electricity very well in general so that's as far as I've got. The computer case is sitting on the carpet - theoretically it's sitting on little rubber feet, but in practice those feet sink in and the whole bottom of the case pretty much ends up directly touching the carpet.

I'm asking this question for two reasons: first, I'm extremely curious about what is actually going on here. By what mechanisms can something like this happen? Does this problem suggest I've built the computer wrong somehow, and/or that one of the parts is faulty? Second, I would like my computer to stop crashing all the time when my cat is around. Do I just need a better humidifier? Maybe I should stand the case on something (like a piece of wood?) to electrically insulate it from the carpet and see if that solves the problem? My cat will inevitably rub his face all over the case and all the cables anyway though, so I don't know how much that will help.

Update 1: By sheer luck, I've narrowed down the problem. Today he walked into my room and over to my desk, and right on cue, the computer crashed. However, unlike previous times, this time I was playing a game with music, so I had audio playing. I was able to observe the following sequence:

• The display went blank, then showed a "no signal" message, then went blank again. During this time, the game's audio continued to play as normal, indicating at least the game's audio thread was still running. This took about 5-10 seconds by my estimation.
• The audio began looping, indicating the audio thread had stopped updating its audio buffer for some reason. This went on for about another 5-10 seconds.
• Finally, the computer's fans stopped and the computer began a restart sequence.

As someone suggested, I checked Windows Event Viewer. No system events were logged from during the crash or just before, but there was one from after the restart with the message: The computer has rebooted from a bugcheck. The bugcheck was: 0x00000116 (0xffffd60fd5a4a460, 0xfffff80617c4bc30, 0xffffffffc0000001, 0x0000000000000003). 0x116 seems to indicate a GPU timeout recovery failure, which is consistent with the observed audio behavior. Looking back in the history, it looks like previous crashes had generated an error with the exact same message (including the same hex constants). So whatever is happening, it's almost certainly to do with the display and/or GPU.

Solution 1:

My guess is that your PC is not properly earthed. It should be able to handle the static electricity, especially if it's from a distance. If you built the PC yourself, make sure every piece of metal is connected to the earth. Also, change the mains cable as it might have a defective earth.

Secondly there might be a component in your PC which is making contact with a metal part of the case: a screw not placed well, a stray cable ...

Thirdly, it could also be that there's a problem with the earth of your house: consult an electrician.

About the cat: a moving charge creates an electromagnetic field (EMF). Equipment may be sensitive to that. There's nothing whatsoever psychic about this! However, a properly designed and built equipment should be able to handle EMF's much bigger than that caused by your cat.

If the PC is properly earthed, any static electricity as well as any EMF should go directly to the Earth, and not have influence on the electronic components.

EDIT: Electrostatic induction (or: replying to magic and sparks)

from Wikipedia Image is Public Domain.

Surface charges induced in metal objects by a nearby charge. The electrostatic field (lines with arrows) of a nearby positive charge (+) causes the mobile charges in metal objects to separate. Negative charges (blue) are attracted and move to the surface of the object facing the external charge. Positive charges (red) are repelled and move to the surface facing away. These induced surface charges create an opposing electric field that exactly cancels the field of the external charge throughout the interior of the metal. Therefore electrostatic induction ensures that the electric field everywhere inside a conductive object is zero.

As is easily imaginable, if the charge (= Cat) moves, the charges in the metal surface (=PC case) will move, too, creating a current. If the PC case is not properly earthed, sensitive parts could feel this current.

There won't be any flying sparks since we speak about induction.

Cables

It is also possible that the cat induces currents in sensitive cables such as HDMI / DP. I don't know how a graphic card might react to this, but out of caution I would ensure to use shielded cables (but these only work ... if they are properly earthed).

Faraday Cage

A possibile Workaround is to build a faraday cage around the PC. This cage will receive the electrostatic charge and protect the PC from it. As a quick DIY solution, i'd use a wire mesh, so that cables can pass. The cage should ...again.. be earthed.

Solution 2:

It might be another thing the root cause of your problem, and the cat behavior AND the computer shutdown to be both the effect of this cause. Lucky you, the cat's sensitivity threshold is better, and you can anticipate when your computer will stop just seeing the cat's behavior who is acting in advance. Maybe the cooler from your video card is starting to make a noise (which cat can hear, but humans don't), and this makes the cat curious and goes to check what's there. Or maybe the humidification is too high, and the cat feels anxious and is searching for a better place in the house (just behind your computer). After that, the protection from your computer triggers for the same reason.

Solution 3:

Theory 1: Misplaced ATX standoff

I’ve built and diagnosed computers for years, and this sounds somewhat like an incident I helped a customer with once.

The customer reported that computer worked fine, but if the computer was bumped (or someone with static electricity got near the tower), it would reboot.

Upon closer inspection we discovered that the brass standoffs that connect the motherboard to the case had been misplaced, which caused one of the standoffs to be touching the back of the motherboard.

Theory 2: Rear IO shield short circuit

This is rare now that many motherboards have integrated IO Shields or use shields with a thin layer of foam. However if your motherboard has an all metal IO shield that has any metal protruding parts, it's possible it could be touching something that it shouldn't be. I've mistakenly made this error several times on PC's I've built, only to find the metal tab is wedged in the RJ45 or USB ports.

Admittedly these are both rare incidents. However your symptoms are also rare and suggest some combination of static electricity and a short circuit.

When I've encountered problems like this in the past, the fastest troubleshooting has often been to completely disassemble the computer and then rebuild it. In many cases reseating all the parts fixes the issue. In rare cases you find something that shouldn't be touching something else.

Lastly as others suggested, ensure you are using a grounded electrical outlet and possibly try a new power cord if you have one.