troubleshooting pc psu

[SavannahLion]

My ten+ year old server finally shutdown after nearly nonstop operation. A power outage killed it. I'm not in the mood to transfer the contents of that server anywhere else. The board looks primo, no busted caps that I can see so I'm working from the source and checking the PSU.

I know I have a box of spare 20 pin ATX PSU somewhere I just have to find it. meanwhile, checking the voltages I find pin 8 to be floating somewhere between 4.7 and 4.3 volts. It's not solid at all, no matter how still I hold the MM. I take it this is absolutely not normal behavior? Is the specification supposed to be exactly 5v or is it around 5v?

I short the ps_on pin and it fires right up but the fan sounds wrong. Almost wispy. Not sure if its because the fan is by itself without the case fan noise or what.

[MonMotha]

What kind of load do you have on the supply?  Do you have access to a scope or at least an analog meter?

[SavannahLion]

No neither. Ive always wanted to get one but could never find one within my budget. I've checked eBay numerous times but don't really know what to start with. 

There isn't much load. It's an AMD 500mhz, 2 HDDS, DVD-ROM, Possibly a modem, everything else is on board.

Only the HDD and RAM isn't stock. It's driving me nuts. I'm typing this from my Droid because my daughter has overrun my house with brats. I'm holed up in the game room with my son playing Super Mario Sunshine. Oh.... the horror!

[SavannahLion]

Now my house smells like a nail saloon.

To avoid having my brain cells destroyed, I've retreated to the garage and voila! I found a spare PSU.

I think this one has a flaky harness though. Whatever, pin 8 on this one is a SOLID 7.?v on my DMM. No wavering or floating or whatever. Shorted the appropriate pins and I got a nice solid sounding fan. Did a test swap and the server powered right up.

I guess my trouble shooting is over. The PSU probably burned out. I'll toss it into my junk box and take it apart to see what burned on the board. Maybe I can learn something from it.

least an analog meter?

Wait... did you mean an analog multi-meter? The kind with the needle and a mirror? Yeah, I have an old Radio Shack one. I used it before I got the DMM I have now. I think I still have it in my tool box. The front plastic is scratched to ---steaming pile of meadow muffin---, but you can still read the needle. I thought you meant an analog scope, the kind that used a XY monitor.

What would an analog multi-meter tell me that the DMM can't?

[MonMotha]

I was asking for either a scope (any kind) or an analog multimeter.  Rapid fluctuations are more likely to show up in a meaningful way on an analog meter (the needle will bounce around) than a digital meter (will will just show seemingly random numbers as it samples).

[ChadTower]

Now my house smells like a nail saloon.

Is that like an old west gay bar or something?

[DaOld Man]

Now my house smells like a nail saloon.

Is that like an old west gay bar or something?