Stupid council

[Commander Kinsey]

Somebody dug through a power main when redoing the pavement. The lights dimmed, a computer power supply exploded, and a broken LED light is now working!

[Commander Kinsey]

Somebody dug through a power main when redoing the pavement. The lights dimmed, a computer power supply exploded, and a broken LED light is now working! I'll be interested in how what everything else treated as a brown out caused a PSU to do that. No smell. Just blew the 5A plug fuse. New fuse and there was a big flash inside it, and still no smell, just like a physical short. WTF?

[Ian Jackson]

In message [e-mail], Commander Kinsey [e-mail] writes

Most switch-mode power supplies take constant mains input power. If the mains voltage is lower, the mains input current will be higher - which is probably why the 5A fuse blew. Presumably some other damage also occurred.

[Rod Speed]

But that assumes that the PC was taking far more than 5A at say 80V which is more than a tad unlikely.

Why should that happen if it was happily contuining to run at say 80V until the fuse blew ?

Even a severe over voltage shouldn't damage anything in a PC power supply unless it is very bady desinged.

[Commander Kinsey]

Yes that was my first thought, a higher current. But the lights dimmed for only about a third to half a second, and no other PSUs blew, including identical ones with a higher load.

However what's really odd is no burnt component smell. I haven't had time to open it up yet, but on replacing the 5A fuse, it flashed inside with a big spark and blew the fuse instantly. Again no smell. Only time you get no smell is a physical short. Perhaps the initial overcurrent melted two tracks together so now it's a real short?

[Rod Speed]

Most likely the MOV died due to a spike.

More likely the MOV died and ended up as a short.

[Brian Gaff]

It won't be the council it will be Conway or some other load of el cheapo workers who probably never looked at the plans of the services. Brian

[Commander Kinsey]

Lightways. Fitting streetlamps, you'd think they'd know where the wires they're going to attach to are.

I looked inside the blown up power supply, and can't see anything busted, I threw it in the recycling, it was only a £25 supply 7 years ago. I was interested in what happened to it though. I'm going to assume under voltage caused over current and busted a weak old component.