On Tue, 16 Feb 2016 23:50:38 -0000, M Philbrook wrote:

In article , says...

I have a pile of power supplies which used to power CCTV cameras. They're rated at 12V 1A. They're very light and give out precisely 12V with no load, so they must be regulated switched mode. So why is it when I try to power a 0.15A 12V fan (a 120mm Corsair computer fan), they fail very quickly? The first one started whining and gave out only 0.5 volts after only half an hour, and the second one went pop after half an hour. I've had two of the others powering door
entry RFID coils and the door solenoids and they've been happy for a few years.

Most likely bad caps , that is most common failure mode for them.

But for two of them? When another two (of the same age from the came camera set) have worked for a couple of years powering door locks?

I've opened them up, this is what they look like. I can see the power transistor in the top one (the one that whistled and produced bugger all voltage) has been warm enough to discolour and crack the yellow wax stuff (ringed in green), but the caps look fine. In the one that went pop, a fuse has exploded (ringed in red).
https://www.dropbox.com/s/q1sc56tx0vtmzuv/PSUs.jpg?dl=0

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40,000 Americans are injured by toilets each year.