Replacing an IBM XT power supply unit with an ATX one

[boggit]

Hello all!

Important disclaimer: I am very new to fiddling around with computer hardware, and I know more or less nothing about how to deal with electricity in this (or, well, any) context.

I've been considering replacing the PSU in my IBM XT with a more modern power supply, mostly because the sound from the fan drives my significant other crazy and she has made it clear that I soon have to make a choice to either keep her or keep my vintage computing hobby, unless I can find a way to make the computer run more silently.

I found this solution available for purchase on tindie.com. It seems to be the answer to my prayers, but I do have some questions that I have a hard time figuring out on my own:

1. If I have understood it correctly, I need to buy the following things to make the ATX4VC solution work:

A. The ATX4VC itself
B. An ATX PSU, such as PicoPSU
C. A power brick with 12V DC and center positive 5.5x2.5mm barrel jack.

Is there anything else I need, that might seem like "goes without saying" stuff for people who are more experienced than I am?

2. Can replace my existing PSU with the ATX4VC (preferably by gutting the innards of my old PSU and place the new stuff there) without having to solder anything?

3. Can I make it work so that I can turn the power on and off with the old orange IBM power switch by connecting it to the ATX4VC solution?

3b. Can I use the old power switch with the ATX4C without soldering anything?

 

[Al Kossow]

"gutting the innards of my old PSU and place the new stuff there"

I guess the tiny market and cost of a 2024 era switching power supply drop-in rebuild for old PCs still isn't viable.
It would be tiny using modern tech (other than the magnetics)

 

[Plasma]

If the only issue is the loud fan, why not just replace that...

 

[jafir]

Here is a modern AT power supply that you can buy new on Amazon, supposedly rated for 400 watts. It feels empty. I have no idea of the quality, but it seems to work.

I would be more tempted to shoehorn something like this into an XT power supply than I would try to make an ATX supply work.



But I agree just replacing the fan is probably a better idea. I’ve got one that is crazy noisy too.

 

[boggit]

If the only issue is the loud fan, why not just replace that...

Hmm, that might not be a bad idea.

If I am to buy a new fan, what specifics should I be looking for to fit the requirements of the original XT PSU?

Here is a modern AT power supply that you can buy new on Amazon, supposedly rated for 400 watts. It feels empty. I have no idea of the quality, but it seems to work.

I would be more tempted to shoehorn something like this into an XT power supply than I would try to make an ATX supply work.

As I am, again, very new to all this, would you mind outlining the benefits of pursuing that path?

Not that I've ever dug around inside an AT power supply unit, but it seems like it would be much more work to gut the old PSU and then gut the AT one as well and put the innards of the latter into the former, compared to fitting the small components of the ATX4VC into the original power supply unit.

 

[jafir]

ATX power supplies (normally) require a soft power on signal via a monetary switch on the motherboard. They are ways to work around it usually, like shorting the green wire to a black wire. AT power supplies work like XT supplies and have normal power switches that are either on or off.

 

[Zare]

If the only issue is the loud fan, why not just replace that...

Depends on what you consider as 'loud'. I have a PS/2 system that has a small diameter fan on PSU. Such a fan will always be heard.
That fan is probably jerky, but it's still only fan on the system, and even if I replaced it with a proper one that won't produce buzzing harmonics the hum will be heard. Those hums are something I really enjoy without.

Hello all!

1. If I have understood it correctly, I need to buy the following things to make the ATX4VC solution work:

A. The ATX4VC itself
B. An ATX PSU, such as PicoPSU
C. A power brick with 12V DC and center positive 5.5x2.5mm barrel jack.

Yes. 12V provides power to picoPSU which turns it to ATX power that has "intelligent" power on, and doesn't have -5V or 3.3V rail operational or can't hold that voltage stably under load. ATX4VC takes care of missing voltages and power button.

Is there anything else I need, that might seem like "goes without saying" stuff for people who are more experienced than I am?

A multimeter. Check and verify the voltage terminals on ATX4VC without connecting it to computer.
Operating a multimeter is easy, red probe goes on voltage, black probe goes on ground, if you have a dial multimeter set it to 20V setting DC, and you should read exactly what you pin into. If you put red on -12 rail, black on ground, it needs to read -12.

2. Can replace my existing PSU with the ATX4VC (preferably by gutting the innards of my old PSU and place the new stuff there) without having to solder anything?

If you have correct cables for ATX4VC then nothing bar chaining stuff is needed. I presume that IBM has standard AT connectors, so you need cable ATX4VC->AT power.
If that doesn't come in package you'll need to buy or strip off two AT power connectors and cables and then screw in those cables to terminal on ATX4VC - again testing everything with multimeter on the AT connector side once it's done.

3. Can I make it work so that I can turn the power on and off with the old orange IBM power switch by connecting it to the ATX4VC solution?

Depends, a lot of PSUs have power switch at the end of a cable, sort of a yoke. You might need to scalpel out the insulation and desoldier the switch.

 

[boggit]

They are ways to work around it usually

Doesn't the ATX4VC take care of those issues?

Depends on what you consider as 'loud'. I have a PS/2 system that has a small diameter fan on PSU. Such a fan will always be heard.
That fan is probably jerky, but it's still only fan on the system, and even if I replaced it with a proper one that won't produce buzzing harmonics the hum will be heard. Those hums are something I really enjoy without.

Yeah, without any humming at all would definitely be ideal.

Yes. 12V provides power to picoPSU which turns it to ATX power that has "intelligent" power on, and doesn't have -5V or 3.3V rail operational or can't hold that voltage stably under load. ATX4VC takes care of missing voltages and power button.

Excellent!

A multimeter. Check and verify the voltage terminals on ATX4VC without connecting it to computer.

Noted. Thank you!

If you have correct cables for ATX4VC then nothing bar chaining stuff is needed. I presume that IBM has standard AT connectors, so you need cable ATX4VC->AT power.
If that doesn't come in package you'll need to buy or strip off two AT power connectors and cables and then screw in those cables to terminal on ATX4VC - again testing everything with multimeter on the AT connector side once it's done.

Ok, I will send an e-mail to the people behind ATX4VC and ask if that is included.

Depends, a lot of PSUs have power switch at the end of a cable, sort of a yoke. You might need to scalpel out the insulation and desoldier the switch.

What would it look like if that is the case, and what would be the circumstances under which such soldering wouldn't be necessary?

 

[Plasma]

Depends on what you consider as 'loud'. I have a PS/2 system that has a small diameter fan on PSU. Such a fan will always be heard.
That fan is probably jerky, but it's still only fan on the system, and even if I replaced it with a proper one that won't produce buzzing harmonics the hum will be heard. Those hums are something I really enjoy without.

It's not a 1U server...the fan is going to be 80 or 90mm. Plenty of quiet fans in that size, especially if you are switching out an AC fan with DC.

 

[cjs]

I guess the tiny market and cost of a 2024 era switching power supply drop-in rebuild for old PCs still isn't viable.
It would be tiny using modern tech (other than the magnetics)

The ATX4VC and a PicoPSU are pretty much exactly that:

 

[cjs]

First, are you sure that the issue is your fan and not your old HDD, if you have one? Those old HDDs are pretty loud, too. You can unplug the internal power connectors for it and start up the machine to see just how loud it is (or, rather, isn't, when not connected).

If I am to buy a new fan, what specifics should I be looking for to fit the requirements of the original XT PSU?

Have a look at the current fan for a CFM rating; this will usually be on the hub. (Or you can probably find this information on-line.) Then you just need a new fan of the same size with at least that rating. Look around for fans with lowish RPM that achieve that, especially ones marked as "quiet," and you will undoubtedly get something much quieter than what you have now.

The modern fan will be DC powered, so you'll need to get 12 V from somewhere for it. If the original fan is also DC, there will probably be a connector providing 12 V for that fan; if the original is AC powered there will be 12 V elsewhere in the power supply you can use, but that may require some soldering.

All that said, you may be better off in other ways just replacing the PSU internals with something more modern, per your original thought. Old PSUs with big electrolytic caps in them like that one generally want those caps replaced at some point, as they will probably leak eventually. (You should probably also get your mainboard recapped, if it's not already been.)

 

[Chuck(G)]

My recollection that the AC fan on the original 5150 PSU (US only) was annoyingly loud.

 

[Malc]

My recollection that the AC fan on the original 5150 PSU (US only) was annoyingly loud.

As was the PAPST AC fans in my 5160 PSU's, A few years ago i bought a same NOS PAPST AC Fan thinking it would be quieter than the fan i had in one of my 5160's, It wasn't cheap and i was very disappointed to find it wasn't much quieter than the one i took out, I have now replaced the AC fans with 12v DC fans and glad i did, Sooo much quieter.

 

[boggit]

First, are you sure that the issue is your fan and not your old HDD, if you have one? Those old HDDs are pretty loud, too.

I'm using a Compact Flash card on a completely inaudible XT-CF-Lite as a hard drive, so yes, It is indeed the fan that is making the noise.

All that said, you may be better off in other ways just replacing the PSU internals with something more modern, per your original thought. Old PSUs with big electrolytic caps in them like that one generally want those caps replaced at some point, as they will probably leak eventually.

Yeah, that is what I was thinking as well. Future-proofing it, as it were.

 

[dekuNukem]

Hi there! Greater of ATX4VC here. I actually designed a PicoPSU adaptor specifically for IBM PC compatibles, which is much easier to set up.

PicoRC/ibmpc.md at master · dekuNukem/PicoRC

PicoPSU adaptor for retro computers. Contribute to dekuNukem/PicoRC development by creating an account on GitHub.

github.com

 

[boggit]

Hi there! Greater of ATX4VC here. I actually designed a PicoPSU adaptor specifically for IBM PC compatibles, which is much easier to set up.

PicoRC/ibmpc.md at master · dekuNukem/PicoRC

PicoPSU adaptor for retro computers. Contribute to dekuNukem/PicoRC development by creating an account on GitHub.

github.com

Hi!

That looks great, but A) it takes up an ISA slot and B) it seems like it would be somewhat tricky to connect it to the standard IBM 5150/5160 power switch, no?

It might be worth it anyway, but the optimal solution for me would be something that wouldn't lay claim to one of the ISA slots, and would make it possible to use the sweet, orange switch.

 

[cjs]

That looks great, but A) it takes up an ISA slot and B) it seems like it would be somewhat tricky to connect it to the standard IBM 5150/5160 power switch, no?

No, you can just run wires over to the original power switch. I am guessing that the "PSW" header can connect to any non-momentary switch (such as the big red one), but in the worst case you could just solder the wires in place of the on-board switch. (That extra soldering should be no issue since you'll have to do a little bit of soldering/desoldering to use the big red switch itself.)

 

[Zare]

It's not a 1U server...the fan is going to be 80 or 90mm. Plenty of quiet fans in that size, especially if you are switching out an AC fan with DC.

I would already replace it with picopsu if it wasn't complicated to pull out. It's an OEM desktop format and to pull out PSU one needs to disassemble everything.
When I get to it I'll open it up and we'll see what we're dealing with, then I can ask here about replacement recommendations.

Yeah, without any humming at all would definitely be ideal.

If you can put a fan that's found on modern noiseless ATX then that works too.

What would it look like if that is the case, and what would be the circumstances under which such soldering wouldn't be necessary?

This is a clean switch

https://m.media-amazon.com/images/I/41F2Ac5Pk5L._AC_UF1000,1000_QL80_.jpg

You just slide in power connectors to those rails and that's it.

The common vendor approach is to take a switch, slide in and soldier the connections, tape everything out with isolation so it's not out in the open. So you get a switch fixed to a power supply.
What's beneath that isolation, I can't tell, so it's not straightforward what you need to do until you check that part out.

First, are you sure that the issue is your fan and not your old HDD, if you have one? Those old HDDs are pretty loud, too.

That's very true. The entire characteristic sound of my lifelong XT is its Seagate drive. Nothing else moves bar it.
I mentally associated that HDD startup sounds with the machine startup. I know at what 'beat' to expect video to come up on screen.

 

[Zare]

P.S. since I gave a multimeter recommendation, what I wrote is OK for picoPSU, for true AT power supply, provide some load on 12V rail first or else it might damage itself.

 

[dekuNukem]

Yeah it does take up an ISA slot, but I wanted to keep the installation completely non-destructive for people who don't want to modify their machines.

You can indeed hook up the Big Red Switch to it! I wrote about how to do that in the second half of the guide.