My computer glitches when I get out of my chair

Miscellaneous and Personal Stuff I Must Share
1

Too odd a thing to not share. But don’t worry, the mystery will be revealed.

I recently upgraded my video card and monitor, with the monitor running at a pretty high pixel rate: 3440x1440 @ 165 Hz. It’s been pretty reliable, but noticed that every so often I’d get a black screen, which would come back in a second or so. Audio (which goes through the DisplayPort cable) also cut out.

It’s been pretty rare and I didn’t have a clear repro scenario, but it never seemed to happen when I was in the middle of using the computer. Just when something… changed. Couldn’t quite pin down anything further though.

Tonight my cat was being rather naughty and I got out of my chair to discipline him. Glitch! Didn’t quite think much of it, since it’s pretty random overall. I sit down again and almost immediately the cat has gotten into trouble again, and I get up–another glitch! This time the coincidence sparks an idea, however unlikely: getting out of the chair is the cause.

I try a few more times and while it is not a guarantee, it is absolutely causing the problem in some way. Once I notice visual corruption rather than a blank screen; probably an indication of just a tiny glitch rather than something that would reset the screen connection.

I run some web searches. I’m not the only one with the problem, but almost all the responses are dismissive. Reinstall the OS. Update the BIOS. Check your drivers. Etc. All useless. I know it’s a hardware problem of some kind. The symptoms are somewhat variable–sometimes there’s a visual glitch, while for others the whole computer resets.

Some suggest that something is loose. But I bump my computer around a bit and it’s fine. Only getting out of the chair is a problem. It’s not static electricity, either.

Eventually, I find the answer: the gas cylinder is known to cause an electromagnetic spike! It’s even listed as a known problem on the DisplayPort website:
https://support.displaylink.com/knowledgebase/articles/738618-display-intermittently-blanking-flickering-or-los

Surprisingly, we have also seen this issue connected to gas lift office chairs. When people stand or sit on gas lift chairs, they can generate an EMI spike which is picked up on the video cables, causing a loss of sync. If you have users complaining about displays randomly flickering it could actually be connected to people sitting on gas lift chairs.

The page even links to a whitepaper from 1993 investigating the phenomenon:

Well yes, I have a Steelcase office chair with a gas lift system that springs back a bit when I get up. Somehow–and I’m not exactly clear on why–this emits an electromagnetic pulse, which couples with the nearby monitor cable, interfering with the transmission for a moment. The monitor notices the errors and resets the connection.

While my chair isn’t new, the higher-speed interconnect to my monitor is probably more sensitive than the previous one. And so it wasn’t a problem until now.

Now I need to work out a fix. I have a feeling it’s going to involve tinfoil.

2

I wouldn’t recommend trying to put tin foil on the cat.

3

He is trying to discipline a cat, so he’s used to futile endeavors.

4

Isn’t there some sort of crustacean that can generate X-rays by snapping its claws? I’m guessing it’s something like that.

5

I have a Steelcase chair with a gas lift system and it springs back a bit when I get up and I have never experienced this problem. And, my chair is about two feet (maybe less) from my PC.

Not saying you are wrong. It does seem odd though.

6

Missed edit:

My PC has two monitors and both use displayport cables.

If you really think this is the problem invest in some good displayport cables and see if it helps. They should be shielded (I think).

I’d recommend Monoprice as a place to buy such things. I’d seriously caution you against going to a place like Best Buy for them.

7

If I get a static shock from the metal on my computer chair, my work laptop will make the Dunk-Dunk! noise like when you plug/unplug a USB device. I am not in contact with the laptop (which is on a wooden table) the the time since my hands are on the chair arms pushing me up. But the laptop still reacts to the static output a couple feet away each time.

(My home desktop PC doesn’t care despite being a few feet away from my work-at-home station and me using the same chair for each)

8

You can also buy ferrite beads that clamp onto the cable. They should help filter out EMI spikes and interference from other electrical devices, if there is any of that.

9

I never learned how those things were supposed to work. Since they were there I presumed they had a use but always seemed a little useless to me. (go with the engineers who put them there and not my feels)

10

The cables are fairly high quality–at least they seem to be. Gold plated, braided cover, allegedly shielded, etc. Though they are one of those random-word-generator brands that you see on Amazon. So who knows.

Didn’t experience the problem (with the same cables) until I got the new card/monitor. It’s also in HDR mode, so it’s a significant increase in bandwidth over what I had before. I expect that it’s just more sensitive now.

Ferrite beads might be worth a shot.

I hadn’t heard about that one. But I know that peeling scotch tape can produce x-rays. There are a lot of odd phenomena like that.

I have a radio spectrum analyzer sitting around somewhere. Maybe I can pick up the burst on that if it’s broad-spectrum enough.

11

Ah, I found it, the pistol shrimp. No mention of X-rays in the quick perusal of articles I looked through, but it does produce a bubble of plasma.

12

I learned from studying for my amateur radio FCC license. Ferrite cores are inductive when wound (or in this case surrounding) with current-carrying wire, meaning that they resist changes in current.

13

In principle, yes, but it’s hard to see that the effect would be very large for only a single winding, which is how they’re usually installed.

14

I was going to blame the cat.

15

Tangential trivia tidbit: The Pistol Shrimps is a documentary that follows Aubrey Plaza’s all-woman recreational basketball team in their quest for a championship.

16

In the middle of winter, he gets incredibly staticky. Just petting him in a dark room looks like a Tesla coil. So far he hasn’t zapped any electronics, though.