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AT PSU failing

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HVPaul

Fri Jun 04 2010, 05:14PM

Registered Member #2321 Joined: Fri Aug 28 2009, 05:13PM
Location: Boston, MA
Posts: 34

I have this old PII IBM computer from late 90s whose PSU seems to be failing.
Getting odd ripple in the video output and all those tell-tale signs (checked, not a videocard/monitor problem).

I'm aware that electrolytic Caps in those supplies eventually dry out resulting in odd output artifacts.
Could this be the only cause of the oddities? I'd imagine a major semiconductor failure would result in pretty nasty results.

What should I be on lookout for if I want to extend its life?

wylie

Fri Jun 04 2010, 07:45PM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

Extend it's life? Dude, just pop an ATX supply in there. Or replace the caps in the AT PSU.

GeordieBoy

Fri Jun 04 2010, 08:51PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

If the caps are on their way out it will usually start to misbehave when the ambient temperature is very low, or when the PSU has just been powered up. This is when electrolytic capacitors are cold and their ESR is maximum.

If electrolytics are drying up or near the end of their functional life the ESR may exceed that required for the supply to start up successfully. In which case you will probably find that one day the supply just won't come on, or it will continuously power cycle but never start up properly.

This happened to an old PC of mine back in January this year. As it happened I had a replacement PC, so I just left the old PC next to the radiator for an hour to warm in gently then applied power. Bingo! It started up, I copied all of the essential content off, and then abandoned the old PC.

It's not worth messing around inside the supply changing capacitors, (and possibly risking your life!) just change the whole PSU out for a known good one. Or back up your data like I did and retire the old computer.

-Richie,

wylie

Sat Jun 05 2010, 04:47AM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

retire the old computer

Right? Is the work it does even worth the electricity it uses?

Steve Conner

Sat Jun 05 2010, 11:14AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You could say the same for a modern gaming PC.

Or my once-high-end 3GHz P4 that used nearly 200W just idling.

An AT PSU has a different connector and different voltages (no 3.3) so you can't easily replace it with an ATX one.

10 years is a pretty good life for a computer, it's about 175 in human years.

wylie

Sat Jun 05 2010, 08:08PM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

An AT PSU has a different connector and different voltages (no 3.3) so you can't easily replace it with an ATX one.

Different connectors? Like that would stop anyone on this board. Slice'n'Splice Baby!

And about the 3.3v rail: if he's running a machine that uses an AT supply, then he doesn't need a 3v rail. To be honest, i thought my one remaining AT supply had a 3v rail, because it also had orange wires.......i'd never tested it though, until i started writing this post.....orange is just another 5v rail in the AT. Good thing I'd never tried to use it for 3v

EDIT: Newer ATX specs get rid of the -5v rail, so that puts the whole idea out the window.

You could say the same for a modern gaming PC.

Except i can play modern games on that PC, so yeah, its worth the electricity costs. And yeah, that idling power sucks, and if i was ever away from my computer for more than 5 hours, i'd definitely turn it off. Well, if my monitor wasn't on it's way out, then i would. (If i let it get cold, suddenly it can't drive the tube at any Res higher than what it uses for the "Monitor Unplugged" message. Guess how i get it to warm up? Yup, make it sit on that screen. Have to switch the input every 2minutes or else it goes back to sleep. Only a matter of time before the filament completely dies, and i get myself a sexy new flyback

)

HVPaul

Mon Jun 07 2010, 01:42PM

Registered Member #2321 Joined: Fri Aug 28 2009, 05:13PM
Location: Boston, MA
Posts: 34

I might get the AT->ATX cable converter if that has the necessary splits.

The repairing bit is just for fun right? :)

I don't actively use this PC, it's among ones that I use for special purposes like for
gaming of the era (3Dfx/Windows 98/DOS)

Renesis

Mon Jun 07 2010, 02:56PM

Registered Member #2028 Joined: Mon Mar 16 2009, 08:13PM
Location: Norway
Posts: 319

HVPaul wrote ...

I might get the AT->ATX cable converter if that has the necessary splits.

The repairing bit is just for fun right? :)

I don't actively use this PC, it's among ones that I use for special purposes like for
gaming of the era (3Dfx/Windows 98/DOS)

If the computer fails or you decide to scrap it, you can still play dos games with DOSBox. Works like a charm on vista.

HVPaul

Mon Jun 07 2010, 03:49PM

Registered Member #2321 Joined: Fri Aug 28 2009, 05:13PM
Location: Boston, MA
Posts: 34

DOS Glide emulation can be very tricky.

Until there's perfect DOS emulation solution I'll keep this junker around :)

Renesis wrote ...

If the computer fails or you decide to scrap it, you can still play dos games with DOSBox. Works like a charm on vista.

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