You better swap it (the PSU)since it's easier to change it than open it and swap electronics.Still,if you said they fit you opened the PSUs?

I would not want to see you dead. Seriously.

I doubt old PSU capacitors could pack such punch and it should take only a minute to leak the energy after power off. Something I do additionally (more for motherboard then psu) is to turn on unplugged system to suck the last watts. Should be easy to not short big capacitor during manipulation. Once unsoldered from circuitry you can measure the load. If there is something left discharge it with some mildly resistant material.

I've opened and cleaned or repaired PSU's many times, even the old large L shaped AT's.
If its been sitting for a couple of days then in my experience you are pretty safe.

Generally you can just get a multimeter and touch the probes to the cap's contacts on the underside of the PCB to discharge it. You should see the voltage drop as the cap discharges, quite quickly. I usually just check the largest caps, usually only two or three of them.
I wouldn't use a screwdriver as you run the risk of it arcing, sending sparks onto your skin or your eye, or melting the screwdriver if its small enough.

However all the PSU's I've opened haven't had any dangerous charge in them. If you're worried, get a pair of insulated gloves.
I read somewhere that most power supplies used in PC's, even quite old ones, have bleeder resistors in them to drain caps almost instantly after the power is turned off. Some cheap chinese ones lack these though.

CRT monitors are very dangerous, they can store huge voltages for a long period of time. They're not to be trifled with unless you're sure of what you're doing. But I think PSU's aren't so bad as long as you take a couple of basic precautions.

A PC PSU will drain all the charge out of the main caps in a matter of seconds. They do have bleeder resistors specifically for that purpose, and even without those, the losses through the rest of the circuitry will take down the charge pretty quickly.

Basically, it'll be safe in the time it takes to get all the screws out and jockey the top half of the case off, as long as you don't do something stupid like work on it when it's plugged in.

As everyone has already stated but these older power supplies don't store much compared to a CRT. If you want to be sure that it is drained then just hit the power switch when the system isn't plugged in and let the board do the rest for a few seconds. The same works on CRTs but you best wait longer before messing with them.

> If you want to be sure that it is drained then just hit the power switch when the system isn't plugged in

A broken power supply might not drain the capacitors in this case.

However, usually there are discharge resistors that work within hours. If they are ok.

There's probably some procedure for discharging them like the one for discharging the power from an original Mac before you start fiddling around with the CRT. I'd do a google search. There's enough hardware sites out there that you'd probably get a lot of hits.

Use a larger resistor to decharge it.

We went over this in this thread a while back:
Cleaning a PSU fan

Well, I didn’t die, and it was easy enough. There was a bit soldering required but nothing fancy.

Here’s the shell; it’s an odd shape with a side switch so not easy to replace. It had a bad cap hence the no-workie.

Donor guts from a standard AT PSU:

Installed. It’s a nice little case so was worth the effort of saving.

why the need of L shaped thingy?
what was they thinking when they design it?

Joey_sw wrote:

why the need of L shaped thingy?
what was they thinking when they design it?

It needs to clear the motherboard, the case isn't wide enough to have a standard rectangular PSU casing.