Once a typical PC power is unplugged, is there any danger of receiving a shock while disassembling it? Are there typically high voltages stored that one should be aware of?
context: removing a cooling fan from an obsolete but functional power supply before recycling.
Safety note to readers: this is a very general question, and the answers will indicate general guidelines about typical power supplies. Observe caution and refrain from performing any activity (such as touching wires or components with your bare hand) that you have not confirmed as being safe in your circumstance.
Answer
Assume: Typical PC power supply = AC mains powered.
There is a short term risk of electric shock from capacitors - principally the two large capacitors used in a "half bridge' arrangement in many PC supplies. These are arranged in such a manner that the supply may be switched between nominal 230 VAC and 110 VAC easily. These capacitors will happily kill you if you let them.
Discharge time for main capacitors is usually seconds with a supply designed to do this.
It can be minutes.
Worst case you MIGHT expect hours.
You'd be most unlikely to find them alive after a day. [If you do, note the brand and buy them in future].
In any case, when dealing with large capacitors that have had high voltage on them I will short them with a piece of wire or screwdriver tip etc.
Note that some capacitors will "recharge themselves" partially due to dielectric absorption. This can take place over minutes and can be exciting. Not usually a major issue but be aware of it.
"The book" will say you should use a resistors, insulated probes and safety glasses.
Using an insulated screwdriver tip, turning your head, shutting your eyes and flinching will usually allow you to "safely" discharge "rather large" capacitors with HV still on them (as long as the source of the HV has been removed) but it can be hard on the nerves, you can get spattered with bits of screwdriver tip, it can make it hard to undo screws in future and the insurance company may refuse to pay your widow. ie use common sense. (Long long ago I did this with 1000 Volts on a cap and the supply still connected "not quite on purpose" - definitely not recommended. The screwdriver tip needed re-grinding :-) )
Other caps of note are the smaller X caps across phase - neutral and the Y caps from either mains lead to ground. These are usually high quality non polarised and MAY happily hold charge for a long time - test discharging them is a good idea. These are usually not large enough to kill (YMMV) but they can hurt badly, and reflexively jerking your hand onto something sharp, hot or live is a risk.
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