A few days ago I did "a total conversion" from ATX to AT by unsoldering the cables from the inside of the AT power supply and the ATX, and soldering them on the ATX, main switch included. Also pass the ATX board to the AT case.
So far so good, the change is not noticeable.

I recapped some of my AT power supplies - 3 so far, but planning on recapping all of them. The tantalum caps on some of these are ticking time bombs. I won't be switching to ATX PSUs any time soon.

Even if I got a couple of good AT psu that works ok, I'm using an Enermax 2003 ATX one that has the -5V line because I might have been unlucky but I've got a 386 mainboard that seems to need that or maybe the whole config prefers having that. Strangest things happened to me without that voltage rail like the vga output slowly fading to black, random crashes etc.. I think the best solution might be a good modern one with old molex connector but has been tested from serious reviewer for retro components, then adding the ATX to AT adapter and possibly with a well built -5V line mod. But lately I was also thinking to a Pico PSU and adding the adapters/mod.

alfer wrote on 2020-09-25, 20:19:

I do want to put a YMF71x card in my MMX at some point and heard that it requires -5V.

Definitely not true. I constantly use YMF71x cards with newer PSUs that don't have -5V and never had any issues.

bloodem wrote on 2020-09-28, 11:27:

alfer wrote on 2020-09-25, 20:19:

I do want to put a YMF71x card in my MMX at some point and heard that it requires -5V.

Definitely not true. I constantly use YMF71x cards with newer PSUs that don't have -5V and never had any issues.

Actually your right!
I've got a YM F719 and thought, oh didn't realise they required -5v, should keep that in mind.
Accept that Socket 8 PC already has a Corsair RM550x

pentiumspeed wrote on 2020-09-26, 15:02:

Shamino, […]
Show full quote

Shamino,

Please show me photo of the Compaq server power supply, the label and another photo of the motherboard connectors please. That's three photos.

Compaq server power supply is what I'm look out for.

Cheers,

I came across it recently, sorry it took so long to post photos.
Maybe I should have just replied with a PM but the forum only lets me attach 1 picture if I do it that way.

This is from a Proliant 800 with an LPX dual Pentium Pro 440FX motherboard.
Since the "P5" connector might be something unusual I showed a closeup of it. I can probably hook it up and check voltages on those pins if you need that info.

So people are saying that the common smaller size is LPX?
That's ironic because this PSU came from an LPX case. It's not a fat cube like the previously shown Baby AT but it's not the "normal" size.
All my Baby AT cases use LPX, but my LPX case doesn't.

What is not pictured is the front panel of power button and LED, please take pictures so I can help you set it up so you can switch it on or off.

Standard AT 2 connectors are standard on this and PSU came from both Proliant 800 (Pentium Pro dual socket using LPX motherboard, basically cheap server) and Prosignia 200.
The other connector is for LED status signal through to the front panel with switch, and extra power wires for 3.3v, power signal one of wire should turn PSU on, active low by grounding, other one is push button signal from front panel with LED through the PSU back into motherboard, just like you do with ATX but odd). 280W is not much for a server but perfect for your other projects and PSU is standard mounting holes too.

"Prosignia" is just a catch all brand starting from low end 386sx computer, home computers, to some odd between mid computer and low end server.

Proliant 800:
https://youtu.be/qF5vvVwhMxU

Prosignia 200:
http://mastodonpc.tripod.com/personal/4055.html

Picture of Prosignia 200 motherboard in detail on ebay.
https://www.ebay.com/itm/Compaq-Prosignia-200 … UIAAOSw3INfCr2Y

Cheers,

shamino wrote on 2020-10-20, 01:32:

I came across it recently, sorry it took so long to post photos. Maybe I should have just replied with a PM but the forum only l […]
Show full quote

I came across it recently, sorry it took so long to post photos.
Maybe I should have just replied with a PM but the forum only lets me attach 1 picture if I do it that way.

This is from a Proliant 800 with an LPX dual Pentium Pro 440FX motherboard.
Since the "P5" connector might be something unusual I showed a closeup of it. I can probably hook it up and check voltages on those pins if you need that info.

Nice ! That is a great example of a "specialty PSU". Has AT connectors and voltages but also 3.3v too plus the special ATX connector.
Thanks for sharing!

Prosignia 200 with wirings installed in detail with motherboard visible:

https://articulo.mercadolibre.com.ar/MLA-7519 … age-antiguo-_JM

pentiumspeed wrote on 2020-10-20, 02:04:

What is not pictured is the front panel of power button and LED, please take pictures so I can help you set it up so you can switch it on or off.

Sorry for being so unresponsive, I'm in the middle of moving and pretty distracted. 😀
I did get a picture of the wires going into the power switch and LEDs, attaching it here.
The switch is mechanically latching, so I think it's just a matter of shorting those terminals to turn it on.

Standard AT 2 connectors are standard on this and PSU came from both Proliant 800 (Pentium Pro dual socket using LPX motherboard, basically cheap server) and Prosignia 200.
The other connector is for LED status signal through to the front panel with switch, and extra power wires for 3.3v, power signal one of wire should turn PSU on, active low by grounding, other one is push button signal from front panel with LED through the PSU back into motherboard, just like you do with ATX but odd). 280W is not much for a server but perfect for your other projects and PSU is standard mounting holes too.

"Prosignia" is just a catch all brand starting from low end 386sx computer, home computers, to some odd between mid computer and low end server.

I have a Proliant 800 which is where this PSU is from. I've been going back and forth about whether to keep it or throw it out. It's hard to justify keeping big cases that are proprietary and can only be used for one system which I hardly ever use. It's a Pentium Pro though, so it's hard to get myself to throw it out either. I'm inclined to keep it if I can.
If I can't, then I guess I'll keep the PSU regardless but since it's oversize I'd only be able to use it in an open air testbench type situation.

I never heard of the Prosignia line before. Funny how much it looks like the same machine but the motherboard is definitely different. From appearance I'm guessing they are the same chassis.

I haven't used the Proliant 800 in years. Last time I used it, I remember thinking the PSU was dying, but I would need to revisit that with fresh eyes. I *think* I was getting an overheat warning on the POST screen. I don't remember if the phraseology was pointing at the PSU or if I had some other reason to think the PSU was an issue.
I might have beat up the PSU by installing dual 512KB CPUs. It came with a single 256K and I don't think the 512s were officially supported.

I have 3 "normal" size AT PSUs. 2 of them are from reputable brands. This is the 3rd, most questionable one. Heatsinks are tiny which explains how light it is.
The label calls it a 250W but the PCB is marked "CWT 200PA" which seems to imply a 200W design.
Maybe "Data Well" is a brand owned by "Channel Well" who actually made the PSU, but that's just a guess.
I've had this since buying it at a local computer parts store back around the turn of the century. I didn't have high standards back then.
I have no problem with replacing caps, but if the underlying design is still a firecracker then there's no point. Any opinions on whether this is worth keeping or should just be thrown out? The most important question is how likely this thing is to cause hardware damage.

shamino wrote on 2020-10-28, 11:22:

I have 3 "normal" size AT PSUs. 2 of them are from reputable brands. This is the 3rd, most questionable one. Heatsinks are ti […]
Show full quote

I have 3 "normal" size AT PSUs. 2 of them are from reputable brands. This is the 3rd, most questionable one. Heatsinks are tiny which explains how light it is.
The label calls it a 250W but the PCB is marked "CWT 200PA" which seems to imply a 200W design.
Maybe "Data Well" is a brand owned by "Channel Well" who actually made the PSU, but that's just a guess.
I've had this since buying it at a local computer parts store back around the turn of the century. I didn't have high standards back then.
I have no problem with replacing caps, but if the underlying design is still a firecracker then there's no point. Any opinions on whether this is worth keeping or should just be thrown out? The most important question is how likely this thing is to cause hardware damage.

This is a really skinny CWT. With that 28 size main transformer it's about 150W max output. A few transistors forming a sensing/comparator for short circuit and overvoltage maybe (Around Q5, Q6 with resistors around them ).
Good for testing HDDs maybe or junk mobos if nothing else is around.