[LiveBrianD]

This morning, I found my alarm clock was dim and my PC's surge protector light was blinking 'unsafe voltage'. A multimeter found that the voltage was 70V (normally ~120-122V). (note: I found this about half an hour after it started, and I unplugged the PC) Another PC in the house was off but plugged in (with NO surge protector, though it suffered no damage). Do surge protectors usually just shut off the output when the voltage is too low? (my laptop was plugged into it, and the battery charging/plugged in light was turned off) Also, can too low of a voltage damage a PC if it's on? (as I said, one PC was plugged in, and it lacked a surge protector, but was completely fine)

[coastie65]

Sounds like good ol California utilities. The one that did not have the surge protector is the one to worry about. When the power comes back up, there could well a surge that will fry things ( did that to my Commodore 64 years ago ). To my knowledge, low voltage won't hurt anything, just prevent it from running.

This post has been edited by coastie65: 30 October 2011 - 02:07 PM

[LiveBrianD]

I forgot to mention - I unplugged that PC too (shut off the power strip actually). The power flickered a few times, then went out, and an hour later came back on. Somehow my router was still working with the low voltage - I checked PG&E's site for outages. The microwave's clock was ok, and the stove worked, but the smartmeter and clock were freaking out (lighting up all digits on the screen).

[coastie65]

We're okay althought Virginia Dominion Power is buying power from outside. They still have the two Reactors shut down at North Anna since the earthquake. Everything has checked out fine but the NRC is dragging their feet on allowing a restart. Bunch of idiots trying to keep the plant shut down. It isn't far from the epicenter of the earthquake but it faired well and all the safety things worked as advertised ( actually worked too good as they had a premature shut down ). Still having aftershocks up there ( have felt a few down here, barely ).

[LiveBrianD]

This was just a very minor outage - only part of this town (the neighbors also had problems, but a friend on the other side of town was fine).

[coastie65]

Probably a distribution thing of some sort.

[mjd420nova]

It would be strange for an under voltage to cause problems with almost all of the normal consumer products. Industrial and commerical equipment is another story altogether. Most of that equipment is protected with a UPS system, but on a much grander scale that you might think. Most UPS specs give a dropout voltage that varies from unit to unit. Anything under 95 volts begins to have serious regulation problems for power supplies and they will crowbar or stop any output. For those who want to experience the event, just set your normal voltage at the power connection to 220 volts. Same result, the voltage input will be halved. It used to be a teaching tool when we taught IBM PC diagnostics.

[LiveBrianD]

Would a switching PSU rated for ~100-240V work at 70V at all?

[coastie65]

I wouldn't think so. or not very well to say the least. It would definitely be power starved. Then again, when you think that 120v or 240 is stepped down to some low voltages at the connections ( +12v on the Video card for instance, although I think it is only 5v on the bus ).