3 ms·

Last night I had a lightning strike nearby and one of two displays blanked for a second. It's behind a UPS and a good surge protector. Likely some EMI/RFI get

by topspin 6mo ago

Last night I had a lightning strike nearby and one of two displays blanked for a second. It's behind a UPS and a good surge protector. Likely some EMI/RFI getting into the power and/or display cable of the monitor itself, toppling digital circuits in the panel and waking up the watch dog. The same display has also blanked in the infrequent case where I've discharged static on the mouse: the cables are all parallel, so they'll couple and bounce the panel ground plane, with the same outcome. These devices are built to the edge of performance margins. Throw in some high voltage transients and things flip out. I think displays are particularly susceptible due to long cables, large surface area and unavoidable shape of common displays: they're effectively patch antennas. The furniture static case is amusing: I imagine some foam cushions can cause millions of tiny static discharges in parallel when they expand. This will flow through the metal stand to "ground" and probably make a VHF range RFI spike (based on the size of a typical chair frame.) Common 24-27" display panel geometry just happens to be in the same neighborhood... Adding ferrites to cables, as I see suggested several times, might help. You could also get unlucky and make it worse: choke a line to just the right length an it becomes a better inductor/antenna. Electricity is fun.

b112 6mo ago
My understanding is it's the piston and gas, undergoing rapid decompressor.
- shmeeed 6mo ago
  That's what I understood from the article as well, but commenters below say they fixed it with a cotton cushion. That rules the piston out.
  - b112 6mo ago
    It's possible there is more than one cause. My chair has a super thin, almost no cushion, so it's not the cause here I think.
    - shmeeed 6mo ago
      If I had to guess, I'd say it's probably the cover, not the cushion.
zootboy 6mo ago
> It's behind a UPS and a good surge protector. To be clear, neither of these things are intended to address EMI/RFI. Most consumer-grade UPSes directly pass the AC power through when not on battery, so any noise on the lines will also pass through pretty much untouched. Surge suppressors are just MOVs (metal oxide varistors) and a circuit breaker. If the line voltage rises too high, the MOVs try to shunt the voltage. But if the EMI's peak voltage is below the MOV's trigger threshold, it will do nothing and the EMI will pass straight through.

by topspin 6mo ago

b112 6mo ago

My understanding is it's the piston and gas, undergoing rapid decompressor.

shmeeed 6mo ago
That's what I understood from the article as well, but commenters below say they fixed it with a cotton cushion. That rules the piston out.
- b112 6mo ago
  It's possible there is more than one cause. My chair has a super thin, almost no cushion, so it's not the cause here I think.
  - shmeeed 6mo ago
    If I had to guess, I'd say it's probably the cover, not the cushion.

zootboy 6mo ago

> It's behind a UPS and a good surge protector. To be clear, neither of these things are intended to address EMI/RFI. Most consumer-grade UPSes directly pass the AC power through when not on battery, so any noise on the lines will also pass through pretty much untouched. Surge suppressors are just MOVs (metal oxide varistors) and a circuit breaker. If the line voltage rises too high, the MOVs try to shunt the voltage. But if the EMI's peak voltage is below the MOV's trigger threshold, it will do nothing and the EMI will pass straight through.