This kind of discussion comes up every once in a while in this forum, and I find it quite puzzling. What exactly are you trying to achieve by doing this? A new power supply isn't inherently "safer" than an old one, yes the old caps may have aged but what really matters is if it was well designed or not, with adequate protections and so on. Replacing with a modern unit can be a source of problems:

• cost of the PSU itself + multiple adapters for -5V, SATA -> Molex, ATX-AT, etc. especially if you're going to do the same on several systems
• lack of strong 5V output, in particular for hungry Athlon XP systems
• very high current output on the +12V of newer units can spell trouble if you have a short, as the protection will take longer to engage vs. older lower current units
• use of multiple (potentially dodgy) adapters can lead to poor connections and melted connectors or components

So, with that in mind, if you have some basic soldering skills (which you probably have if you intend to build those adapters yourself) it doesn't take much effort or money to refurbish the existing units or used ones from that period (mostly new caps and maybe the fan). In particular, I bet the PSU on the Dell PPro is of good build quality and a refurbish would be ideal, especially considering you wouldn't even have to deal with adapting the proprietary connectors.

Regarding the -5V thing, only a small subset of ISA sound cards use this, are you sure you have one that will require it? Not sure about modems, I haven't used an ISA one since like 1997.

I mean, sure, it's worth a discussion.
I'm not running Athlons, so I don't need mega 5v+ rails.
I already have the adapters, (already bought) so it's not that big of a deal.
I'm using some standard ATX Corsair Bronze power supplies. Not the best, but not known to be like 0ff-brand either.

I'm not too big of a fan of trying to refurbish an old power supply and hunt down all the parts and what not. I could do that, but I'd rather just re-pin an ATX adapter.
As far as why replace the power supply in general? Yes, my old ones work, but I've heard anecdotal stories of PSU's letting the smoke out of people's machines. Also, I thought the consensus was that the modern power supplies are better built than the vintage ones when they were new. They also have on-board safeties that actually saved my bacon on my K6 board when I plugged the 24 pin into the 20 pins the wrong way. It didn't turn on. The PSU was smart like that.
Thought being if I setup all my adapters and there's ever a problem down the road, I can just swap out the PSU with a standard ATX supply and be back up in 15 mins.

Lastly, do I *need* the negative 5v? That I'm not always so sure. Maybe I have too many DMA/IRQ's being used on the board now and that's my root issue. It was an elimination of possibilities.
As far as your comment about using old ISA cards. I specifically acquired these systems for the ISA slots since my goal is circa 93-97 computing. ISA was a pretty big thing back then.

Thanks for the input. I'm just looking for a parts list and a diagram of what I'd need to build to get the -5v going. I do believe I can figure it out if i spend a few hours at it,(I'd document and post results here for posterity) but it seemed to be such a throwaway comment for people that 'you can just build one' I'm figuring there's someone who has and can provide a 'cheat sheet' on how to do it.

P-Tech wrote on 2024-08-09, 18:39:

Yes, my old ones work, but I've heard anecdotal stories of PSU's letting the smoke out of people's machines.

"Anecdotal" is the keyword here 😃, I won't try to talk you out of it but the failure modes of power supplies and potential damage to other components is not about "old" vs. "new".

P-Tech wrote on 2024-08-09, 18:39:

They also have on-board safeties that actually saved my bacon on my K6 board when I plugged the 24 pin into the 20 pins the wrong way. It didn't turn on. The PSU was smart like that.

Precisely, that's not a modern feature at all. Any half-decent AT/ATX power supply has short-circuit protection unless we're talking bottom of the barrel stuff... but if you have a short on the 12V line of a modern power supply the protection will take longer to kick in as they can deliver a lot more current before triggering the SCP.

P-Tech wrote on 2024-08-09, 18:39:

Lastly, do I *need* the negative 5v? That I'm not always so sure. Maybe I have too many DMA/IRQ's being used on the board now and that's my root issue. It was an elimination of possibilities.
As far as your comment about using old ISA cards. I specifically acquired these systems for the ISA slots since my goal is circa 93-97 computing. ISA was a pretty big thing back then.

I meant that I haven't used ISA modems since 1997, so I'm not sure which ones require -5V. Of course I use plenty of old ISA cards like most people on this forum 😉. Anyway, for sound cards you can check old threads to know for certain if you need the -5V or not. The ones that come to mind right now are SB 2.0 (CT1350), Media Vision PAS, Roland LAPC-I.

P-Tech wrote on 2024-08-09, 18:39:

Thanks for the input. I'm just looking for a parts list and a diagram of what I'd need to build to get the -5v going. I do believe I can figure it out if i spend a few hours at it,(I'd document and post results here for posterity) but it seemed to be such a throwaway comment for people that 'you can just build one' I'm figuring there's someone who has and can provide a 'cheat sheet' on how to do it.

What all of these adapters do is basically regulate the -12V down to -5V by using a 7905 voltage regulator. I'm sure there are threads with schematics on this forum, but in any case you can always refer to the 7905 datasheet, there is always a section showing typical applications with circuit diagrams. All you need in this case is probably the regulator itself and a couple of capacitors, the datasheet itself will suggest adequate values. The regulator is very simple, it has 3 pins (input = -12V in this case, output = -5V and GND), you add a cap in parallel with the input, another with the output and voila!

Dell Pentium Pro? Do NOT use another atx power supply! Dell in that timeframe had “proprietary” atx-style connectors, but all the pins are shifted (the pins that got excluded from the shift are in a second connector next to the ATX type connector). Attempting a regular ATX psu will at best not work, at worst, fry your motherboard and psu. Good PSUs simply won’t fire up as the power on pins aren’t connected to something to short them.

I have a Dell PPro motherboard. Got it cheap since it didn’t power up with a regular ATX. Fortunately for me there was no damage. I sourced a unicorn power adapter for that plug configuration to ATX and the board works great (ATX plus adapter).

The other issue you might run into is if the board is one of the Intel ones (look for four square chipset chips with intel on them), the bios might be “dead”. Intel, for whatever reason, chose to go with sd-style Bios. After a few decades, they forget their contents. Fortunately, you can reflash them (with a floppy drive & a jumper setting), making them good for another decade or two.

Ah I see you are already handling the power connector issue 😀 Stability issues might be a bios thing, reflash your bios and the stability issues might go away. Worked for both my ppro boards (the other was an older Intel aurora board with regular atx connector)

Also, the more commonly available ppro/dell adapter with sidecar 6-pin connector doesn’t work. I’ve even ordered one supposedly for dell and only realized my mistake when it arrived and I checked the pinout.

Looks like the unicorn adapter is still available. Go to the usual online auction site and search for “ Dell proprietary 20pin 6pin PSU adapter converter”, and if you get the seller from the UK, that’s it. Claims there are two more left. That’s where I got mine and it worked great on my Dell PPro motherboard.

Hoof wrote on 2024-08-09, 20:01:

Dell Pentium Pro? Do NOT use another atx power supply! Dell in that timeframe had “proprietary” atx-style connectors, but all the pins are shifted (the pins that got excluded from the shift are in a second connector next to the ATX type connector). Attempting a regular ATX psu will at best not work, at worst, fry your motherboard and psu. Good PSUs simply won’t fire up as the power on pins aren’t connected to something to short them.

I have a Dell PPro motherboard. Got it cheap since it didn’t power up with a regular ATX. Fortunately for me there was no damage. I sourced a unicorn power adapter for that plug configuration to ATX and the board works great (ATX plus adapter).

The other issue you might run into is if the board is one of the Intel ones (look for four square chipset chips with intel on them), the bios might be “dead”. Intel, for whatever reason, chose to go with sd-style Bios. After a few decades, they forget their contents. Fortunately, you can reflash them (with a floppy drive & a jumper setting), making them good for another decade or two.

It's currently a working machine, so I'm good to go there. I picked it up for like $125 shipped, so it wasn't bad, but wasn't cheap either.
As far as the power supply, I'm just looking to be proactive. I haven't swapped the cables out yet, but I'm already re-pinning with the diagram I found on this site. I'm going to get my Fluke meter out and do one last check to make sure I didn't dyslexic swap the cables, but I'm all over it!

Hoof wrote on 2024-08-09, 20:04:

Ah I see you are already handling the power connector issue 😀 Stability issues might be a bios thing, reflash your bios and the stability issues might go away. Worked for both my ppro boards (the other was an older Intel aurora board with regular atx connector)

I did update/flash the bios, it was one version behind, on the PPro, so I'm good to go there.
I had more issues with the K-6-3 which is super socket 7 and a Via chipset. It's a Tyan board so all the caps were in great shape, but since it's a Via chipset it may never be 'perfect.' It's mostly trouble free though. It's flawless in Win98, dos and peripherals are hit or miss.

That’s awesome 😀 I was attempting to hobble together an adapter myself, then after slicing my fingers a few times (as well as puzzling out the best way to feed a third 3.3v wire to the sidecar plug), I tried the auction site one more time. That’s when I found and ordered the one from the UK seller.

The annoying thing for me was that literally a few months before I had picked up a few old psus from a friend. One of them had a sidecar plug, and failed on my ATX test device. So I recycled it. It was only a few months later when I learned about the Dell psu setup on my just acquired PPro motherboard. I realized I’d likely tossed a perfectly good Dell psu that would have worked natively with the board. Such a facepalm moment!

Correction, it was a 5v wire, not a 3.3v. I wish Vogons let you edit posts 😀

P-Tech wrote on 2024-08-09, 20:21:

As far as the power supply, I'm just looking to be proactive.

I don't mean to annoy you here, but there's no need to be "proactive" about "fixing" a (possibly? likely?) non-existent problem.
Like TheMobRules mentioned, your original Dell power supply is probably of very good quality, if not superb.
Up until the Pentium 3 era, a good number of OEM PSU manufacturers for Dell and HP (among others) used quality Japanese capacitors in their PSUs (e.g. ASTEC, Lite-ON, Delta, Mitac, and etc.) And the PSUs themselves were very solid designs (dare I say even more reliable than modern stuff, since the old PSUs lack APFC, which is a relatively common failure mechanism on moderns PSUs.) So if you have one of those, definitely don't swap it. It will likely last the whole lifetime of the system. Just open it and clean the dust out of it.

On a related note, I acquired an ASTEC XT style PSU for free many years ago off of Craigslist. Was labeled as "not working". Well, it's an XT power supply that expects much of its load on the 5V rail. With no load, it would turn On and turn Off right away. But as soon as I put even a tiny load on the 5V rail, it worked great, as if it had just come off the factory floor. What's particularly interesting here is that I picked up this PSU over a decade ago (around 2010-2012 or so) and had completely forgotten about it after cleaning it from dust and putting it in storage. The guy who gave it to me said he also got it over decade ago (so possibly back in the late 90's.) Then I moved this year and inevitably dug it out. It hadn't seen a stray electron charge all of this time (over 20 years), which is definitely not great for the electrolytic caps. But I opened up the PSU and saw all Japanese capacitor brands, so I wasn't too worried. I thought about taking the PSU apart and reforming the caps. But the PSU was a little more work to take apart than many others I have seen. So I skipped that part and just fired it up. Needless to say, there were no issues, as I expected. It worked fine and gave out stable voltages and very clean output on the 5V rail. Not only that, but I even decided to "abuse" it a little to see how well an old XT PSU like that would do with some short-circuit tests. Needless to say, all of the rails made the PSU shut down instantly when I shorted each one to ground. I also tried something even more naughty: short-circuit from rail to rail. That was a fine pass too and no fireworks. So it goes to show that a properly-designed good quality PSU will go quite far.

It always puzzles me, the holy grail of minus 5 volt. For what... Do you all have a original mono sound blaster, that only works in a 386 or slower machine. Or rockin a LAPC-I. Or still use some obscure modem to dial phone lines???

Hiya!

I encountered an issue recently with my wierdo of a PII/PIII 440BX mobo (https://theretroweb.com/motherboards/s/siemen … tem-board-d1107 without networking). I have suffered so much with this system... instability, CD/DVD, floppy and hard drives not working, and I only had one somewhat working old PSU that had -5v. Recently I upgraded the PSU in my main rig so I have one Seasonic S12 II that I decided to put in this retro PC, but OFC it doesn't want to boot.
I have an ESS sound card, and my mobo might need -5V as well, but I really don't want to go back to that crappy old PSU if possible.

I would like to get a Voltage Blaster (as I have 2 ISA slots, and one is a PCI combo) or maybe an adapter that goes between the PSU and mobo 20pin ATX connector, but I don't know what I should look for (I've heard there was a cool adaptor, but they are now out of stock).

Any tips? Can I go wrong with a Voltage Blaster?

P-Tech wrote on 2024-08-09, 16:35:

(...) So, I figure I'll get -5v going, and eliminate at least one variable. While the Voltage blaster that is available is a co […]
Show full quote

(...)
So, I figure I'll get -5v going, and eliminate at least one variable. While the Voltage blaster that is available is a cool idea, it's not really ideal when you have PC's that only have 2 ISA ports as they have PCI as well. I do specifically intend to have ISA Sound and ISA modem as these were two of the biggest uses I was into back in the day. And I do have a dial-up modem itch to scratch that I'd love to share some semi-reliable ways to get dial-up working over voip. (that's for another day, but 9600bps-14.4 is the target)
I do like the ATX adapater on Tindie (https://www.tindie.com/products/milkfactoryco … er-atx-version/) But they're sold out and no ETA for replenishment.
I've done a fair amount of websearches for what it would take to make my own with a few parts, heat shrink and solder, but there's no real definitive guide. I've seen offhand comments that it's possible and not incredibly difficult, but I haven't found any good directions. I've found generic electrical engineering references, but they're also going into the weeds on design considerations that aren't applicable to my (simple-ish) use. Does anyone have any decent directions that distill what I need to do and how to make this mod? Maybe a link to a good resource? My google-fu has let me down this time.

Yeah, I'm dumb the thing I mentioned is in this very thread, I'm probably on Class A Amnestics 🤣

MoltenEQ wrote on 2024-12-25, 11:24:

Hiya!

I encountered an issue recently with my wierdo of a PII/PIII 440BX mobo (https://theretroweb.com/motherboards/s/siemen … tem-board-d1107 without networking). I have suffered so much with this system... instability, CD/DVD, floppy and hard drives not working, and I only had one somewhat working old PSU that had -5v. Recently I upgraded the PSU in my main rig so I have one Seasonic S12 II that I decided to put in this retro PC, but OFC it doesn't want to boot.
I have an ESS sound card, and my mobo might need -5V as well, but I really don't want to go back to that crappy old PSU if possible.

I don't think you'll need -5v for anything stock on something new as a PII/P3.
Did you plug the ATX power connector in the right way? The clip lines up? I've seen the older board connector is smaller than the new plugs on the wires, so you might have 4 pins overhanging one side.
Secondly, it's an older system, so you're fighting a lot possibilities, and one of them might be time/capacitors and the like.
I've also fought with IRQ/DMA issues myself, and they seemed to be exacerbated when I used a USB keyboard and mouse rather than PS2.
That said, get your system running, maybe a new power supply if you suspect the old one is a problem. Then, yank out all the peripherals you can and let the system run for as long as you used to have issues, let a benchmark loop etc. If you think it's stable, add one card / component and repeat the process. You may find there's a card or accessory causing your issue.

Also, don't rule out CPU cooling, so make sure fans and airflow along with a good contact with thermal paste so you can rule out thermal protection as well.

Your boards look nice! I am currently designing something like this, but with separate 12V and more protection. What is the part number of the male power connector that you have used? I can only find wire-mount version, not board mount.

Got this bad boy ripped out, and now I can get a POST. But the floppy still doesn't work all the time (capacitor issues), and my video card has some funny output in GRUB (it's a GeForce 6200 for digital out). I also saw some sparks and got shocked from my VGA cable. I didn't even know that such high voltages could go through it. I hope the monitor is not killing my laptop through HDMI, and that the electrostatic shocks didn't damage my HDMI VGA adapter or the GPU.

But it turns out that (at least this) ESS cards probably need that -5V.

So, voltage blaster, maybe?

(Also, I'd like to somehow ask for PhilsComputerLab or Necroware to take a look, if I managed to meet them)

Whoa my man, slow down. You’re having all kinds of other issues. You have broken plugged into broken. You can’t diagnose anything.
First, sounds like you’re having monitor issues, they’re about the age to have capacitor problems. Adrian’s digital basement and sometimes Tech Tangents dive into fixing them.
That said, get a newer monitor that’s LCD with a VGA plug and see if you can get a boot.
Try just dos for now, while you’re working the bugs out, Linux for when you got stability.