Power supply bad? Computer won't start, but gets slight power

I have a second old computer I use as the dedicated media computer hooked up to my big screen.  I noticed that a couple of times I would push the power button and it would not go on even though I saw the power light on the card reader go on.  I unplugged it from the surge protector waited a few moments and plugged it back in, hit the switch and it powered up just fine.  I have had to do this several times and now it no longer powers up at all (except for the power light on the card reader).

I put the computer on my bench, took off the side, plugged it in and I hear a low audible, high pitched whine coming from the power supply, but nothing is moving inside the power supply.  I push the power button and the fans spin for 1 or 2 seconds and die.  I think the power supply is shot and I need a new one, but I wanted to confer with some experts to see if my diagnosis is correct before I order a new one.  The present power supply is a 500 watt Antec Smart Power.
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JohnBusiness Consultant (Owner)Commented:
Measure the output of the power supply with a voltmeter. That may tell you.

Old computer = old design = likely bad electrolytic capacitors in the power supply which is likely why it does not work.

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Look at the Electrolytic Capacitors on the mainboard. If you notice them bulging, leaking, or cracking they are bad and the cause. Those capacitors are also used in the PSU, so it is possible that also that is bad.

Clean out all the dust. Maybe your fans are stuck and the system is overheating. Also look at how the heatsink is seated on the CPU. Reseat the RAM. Replace the CMOS battery on the mainboard.
dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
See if you can power up your PSU following the instructions at http://www.instructables.com/id/How-to-power-up-an-ATX-Power-Supply-without-a-PC/

Make sure you have some device connected to the PSU as suggested by the link (CDROM drive, hard disk etc etc).  If the devices don't startup or the fans don't work in the PSU or the PSU doesn't start up it's dead.
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it can also be a low bios battery - check it's voltage - or replace it
it should be 3 V min -  a CR2032 model
ArtG2521Author Commented:
I will check all these things as best I can and let you know.  Also my "bench" is not sophisticated.  It a glorified small table.
can you post the pc model?
ArtG2521Author Commented:
From what I know and the advice you all have given, it seems to be the power supply.  Luckily for this old computer I can get a decent PW for about 50 bucks.  Thanks much.
JohnBusiness Consultant (Owner)Commented:
@ArtG2521 - You are very welcome and I was a happy to help.
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