View Full Version : Rebuilding PSU

April 28th, 2008, 12:30 AM
This weekend I picked up a whole car of IBM parts, including 3 complete systems, all in bits. Unfortunately two of the machines have PSUs that don't work, and the one that did only worked for 3 hours...

I have a PC 63W that spins up, but doesn't power on the motherboard;
an original XT 130W that doesn't even power up;
and a Clone 150W that keeps blowing the internal fuses.

Added to that, my original XT (with clone 150W PSU) also decided to die with an almightly bang :mad:

Luckily I have 3 spare AT PSUs from dead 486 / Pentium 1 cases. Is it possible to use the guts from these to fix the XT PSUs? If so, how?

Terry Yager
April 28th, 2008, 12:51 AM
Luckily I have 3 spare AT PSUs from dead 486 / Pentium 1 cases. Is it possible to use the guts from these to fix the XT PSUs? If so, how?

I never had much (good) luck, but I read on the web somewhere that somebody claims to have done it. YMMV.


April 28th, 2008, 03:12 AM
It's got to be worth a try, it seems the only thing different would be the switch type.

Otherwise I'm going to end up with a big pile of parts to eBay :(

April 28th, 2008, 03:39 AM
Are there no diagrams, schematics of the original IBM XT power supplies, so anyone skilled in repairing high-voltage equipment could locate which items may be at fault? At least I suppose you can disassemble it fully and get to work on the parts, unlike some other power supplies which tend to be sealed shut.

April 28th, 2008, 06:16 AM
I did it for my 5150 last year. I had the 63watt psu in the my 5150, unfortunatly it was not cranking out enough juice to spin up the hard drive I wanted to use, then it died.. ha. So I took a 250watt at psu I had laying around and basically swapped the guts in to the old PSU's case. Worked great, I was nervous the first time I flipped the switch, was paranoid I wired something wrong ;) When I get home, I will take a picture for you.

April 28th, 2008, 07:23 AM
Excellent, thanks! How did you wire up the switch? Apart from that, the conversion seems relatively straightforward. I guess I'll need to make up some new mountings for the circuit too.

April 28th, 2008, 05:08 PM
Sorry for the delay! (in case anyone cared enough and was anxiously awaiting my post) I forgot about this, I had to resume a server support call when I got home from work /curse_VPN/RDP ability. Anyway... the original guts of the 63.5watt psu died, I replaced it with the guts from a working 250watt at psu... I used ample amounts of red-neck engineering...

I did not resize the images, so I hope you have broadband... or a lot of free time to waste.



I soldered the wires to the switch mechanism as the remnants werent long enough that i was comfortable stripping the ends and useing electrical tape alone.
Also notice the voltage regulator switch , I initially forgot to put that peice in and took me 45 minutes to realise why the PSU wouldnt fire up the machine.


notice the brass standoff utilised to keep the PCB from flapping ;)


I would imagine, there being so many PSU's out there that results will vary... and hopefully for the better ;) albeint mine works fine....

I just wanted to add, I realise its a sloppy, dirty hack... but it works =)

nige the hippy
April 29th, 2008, 08:52 AM
And just before you start ripping the guts out of all those PSUs, ...remember the capacitors I sent you...!

Terry Yager
April 29th, 2008, 10:37 AM
I used ample amounts of red-neck engineering...

Where's the duct tape?


April 29th, 2008, 02:36 PM
Where's the duct tape?


I opt'd for electrical tape as I had temporarily /gasp ran out of duct tape when I did the cob job

May 2nd, 2008, 10:11 AM
Excellent pictures, JDT! I like the case standoffs for the PCB mounting especially :)

Just one question though. I've now looked inside my PSU, and the AT type has four wires going to the switch. One black, one white, one brown and one blue.

The XT PSU also had four, but two black and two white.

How did you wire up the XT switch with the AT wires?

Apart from that I think it is straightforward to do...

nige the hippy
May 2nd, 2008, 03:05 PM
US mains,
Black = live,
white = neutral

UK mains
Brown = live
Blue = neutral

May 4th, 2008, 06:24 AM
I know about the colours, but wasn't sure how to wire them up to the IBM on/off switch. Black/White at the top and Brown/Blue at the bottom? Vice versa? Or doesn't it matter?

nige the hippy
May 4th, 2008, 08:44 AM
Whichever of the two is most convenient.

If you don't know the switch, it's best to check which the pairs of contacts are, before you wire a "switchable short circuit" across the incoming mains! I've been unpleasantly surprised before now!

(obviously it's live switched to live & neutral to neutral)