I have a 5 year old SCSI workstation, dual PII 400mhz.

It's running Linux RH8 but that's a moot point since I haven't booted it up in 2 weeks and having just tried to boot it up, I get no response to the power button. No lights, no noise - totally dead.

I am thinking the power unit failed, if so, how does one replace it? This workstation is worth nothing so I don't want to put any significant money in it. Or could it be something else, like the "on" button?

It certainly sounds like the power supply.

That is a power failure, but it doesn't necessarily mean that the PSU is gone.

It could be the fuse, the plug, the socket or any number of things. If you can swap the power cable with another PC (or similar device) easily then it would be worth doing just to check that the cable's not cracked internally (possible but not likely).

Then I recommend testing the wall socket with something else to see if that's working, then checking the fuse, then moving on to the PSU. Make sure that everything's plugged in firmly.

The on button can fail. You can check it by unplugging it from the motherboard, and shorting the two jumper contacts together with a screwdriver (or anything metal). Then remove the screwdriver. This will simulate a push of the switch. Dust or crud between the contacts may also cause a short, so remove any that you see.

Replacing the power supply isn't that hard. The identical-looking connectors are, in fact, identical and each one can plug in anywhere. But Make a note of how the motherboard connections go before you take it out. You need to buy the right type of replacement (AT or ATX) and then it's literally a case of unplugging it, unscrewing it, taking the old one out and then repeat (in reverse) to put the new one in.

The power cable checks out OK and so does the wall socket.

Where is the fuse located?

I removed the case and found out it is very dusty internally. I am going to get a case of air and 'spray' it with that compressed air, especially inside the power unit, I would imagine it's pretty dusty inside because the fan blows air in. I will try to remove the power supply and cleaning it with air.

The fuse is normally in the wall plug; if the power cable works then it's OK.

Fans that blow air in usually produce less dust than those that blow air out; the internal pressure is greater and so dust gets blown out. PSUs don't usually succumb to dust problems but it may be worth a try.

Now that I think about it, it is a fan that blows air out. Strange and sudden failure.

The fuse is located in the power supply not in the wall plug. The hard part is opening the power supply and then locating it. If you are not cafeful the coils or capacitors can throw you across a room. I suggest using a 1 megaohm or 10 megaohm to discharge these components before poking around.

You can use a foot pump instead of costly compress air cans to blow away dust in a computer.

Well, I got it working by shaking it and blowing into it. Hm.

I think this whole computer is a perfect definition of "obsolete". Strangely, dual PII 400 Mhz is stil as fast as day I got it and runs RH 8 nicely.