I'm certainly not an expert.
But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-waste.
Basically if you can easily replace it with a modern PSU don't bother =)

On a side note.
Wouldn't it, with all the expertise on this forum, be possible to design replacement guts for our failing AT and high amp +5v ATX power-supplies?
A new 300w'ish -modular- AT PSU with temp controlled fan? yes please!

bofh.fromhell wrote on 2022-07-26, 14:31:

I'm certainly not an expert. But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-wast […]
Show full quote

I'm certainly not an expert.
But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-waste.
Basically if you can easily replace it with a modern PSU don't bother =)

On a side note.
Wouldn't it, with all the expertise on this forum, be possible to design replacement guts for our failing AT and high amp +5v ATX power-supplies?
A new 300w'ish -modular- AT PSU with temp controlled fan? yes please!

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important.

Anyway, I'd rather use a new PSU, but very few new power supplies have strong enough rails that are important for retro build and no molex / floppy cables.

In Pentium 1 / 2 builds that I have I ended up using more modern PSUs with 120mm fans that run nice and quiet, but again, lack of molex power cables is an issue and SATA-Molex adapters create a bit of a mess.

That Mitac PSU looks like a hardware killer. As a general rule, heavier is better.

blackmasked wrote on 2022-07-26, 14:48:

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important.

Nope. Pentium 4 might be more 12V heavy, depending on the board, but Pentium 3 and Athlon are 5V all the way.

blackmasked wrote on 2022-07-26, 14:48:

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important.

Yes, but you can get strong +12v in any ATX PSU since 2004 or so.
There is however quite a few motherboards in the early ATX years that uses +5v for its CPU power.
Those are the ones that poses problems for modern PSU's.

blackmasked wrote on 2022-07-26, 14:48:

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important. […]
Show full quote

bofh.fromhell wrote on 2022-07-26, 14:31:

I'm certainly not an expert. But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-wast […]
Show full quote

I'm certainly not an expert.
But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-waste.
Basically if you can easily replace it with a modern PSU don't bother =)

On a side note.
Wouldn't it, with all the expertise on this forum, be possible to design replacement guts for our failing AT and high amp +5v ATX power-supplies?
A new 300w'ish -modular- AT PSU with temp controlled fan? yes please!

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important.

Anyway, I'd rather use a new PSU, but very few new power supplies have strong enough rails that are important for retro build and no molex / floppy cables.

In Pentium 1 / 2 builds that I have I ended up using more modern PSUs with 120mm fans that run nice and quiet, but again, lack of molex power cables is an issue and SATA-Molex adapters create a bit of a mess.

P4 wants a ton of +12v where as P3 and Athlon XP want as much +5v as you can give them, the higher end Barton's really do like +25Amps on the +5v rail but with a stripped down setup you can get away with less. (P3 is far more forgiving with +5v Amps as it doesnt draw anywhere as much power as a loaded Athlon XP system can, especially over clocked ones)

This is just my experience and I have a number of these systems, there have been others who have gotten Athlon XP to run just fine with modern ATX PSUs but I have no idea if they are running a lean setup that isn't hogging the +5v rail. I would guess that if they are running a setup with out Spinning Rust or Optical drives/Floppy Drives then the load on the +5v rail would be considerably less, a GPU with its own Power connector would also help a modern ATX PSU deliver the needed +5v Amps.

They're all at least decent. For AT units they usually all use very similar topologies, so you won't find lots of differences unless we're talking about proprietary stuff. You won't need more than 150W when running AT stuff except in extreme cases (very late builds or if you put a bootload of drives or something like that). And all of these units can handle that easily, they won't "kill all your components and set your house on fire".

When it comes to ATX, it depends what kind of rig you're planning to run, but both Delta and FSP are reliable manufacturers.

This is all assuming you are capable of doing some basic refurbishing, i.e. replacing the fan and capacitors (on secondary side at least).

Remember that capacitors can be replaced, but there's not much you can do with a bad design.

TheMobRules wrote on 2022-07-26, 16:29:

They're all at least decent. For AT units they usually all use very similar topologies, so you won't find lots of differences un […]
Show full quote

They're all at least decent. For AT units they usually all use very similar topologies, so you won't find lots of differences unless we're talking about proprietary stuff. You won't need more than 150W when running AT stuff except in extreme cases (very late builds or if you put a bootload of drives or something like that). And all of these units can handle that easily, they won't "kill all your components and set your house on fire".

When it comes to ATX, it depends what kind of rig you're planning to run, but both Delta and FSP are reliable manufacturers.

This is all assuming you are capable of doing some basic refurbishing, i.e. replacing the fan and capacitors (on secondary side at least).

Remember that capacitors can be replaced, but there's not much you can do with a bad design.

I'm more concerned about AT PSUs to be honest, first 3 on that list. I do have a 486 and a couple of Pentium 1 builds and PSUs used to power them all don't give me much confidence.

I'm capable of refurbishing them, but as you said yourself, it may not be worth doing if it's a badly designed PSU. However, I don't have the know how to come to this conclusion just by looking at the insides. Weight test may be a good indication, as usually heavier equals better quality, but I'll need more than that. ;]

By the way, what do you guys do whan it comes to using modern PSUs in retro builds that lack molex/floppy connectors? Do you use adapters or do you desolder/cut everything unnecessary and replace them with molex?

blackmasked wrote on 2022-07-26, 16:42:

I'm more concerned about AT PSUs to be honest, first 3 on that list. I do have a 486 and a couple of Pentium 1 builds and PSUs u […]
Show full quote

TheMobRules wrote on 2022-07-26, 16:29:

They're all at least decent. For AT units they usually all use very similar topologies, so you won't find lots of differences un […]
Show full quote

They're all at least decent. For AT units they usually all use very similar topologies, so you won't find lots of differences unless we're talking about proprietary stuff. You won't need more than 150W when running AT stuff except in extreme cases (very late builds or if you put a bootload of drives or something like that). And all of these units can handle that easily, they won't "kill all your components and set your house on fire".

When it comes to ATX, it depends what kind of rig you're planning to run, but both Delta and FSP are reliable manufacturers.

This is all assuming you are capable of doing some basic refurbishing, i.e. replacing the fan and capacitors (on secondary side at least).

Remember that capacitors can be replaced, but there's not much you can do with a bad design.

I'm more concerned about AT PSUs to be honest, first 3 on that list. I do have a 486 and a couple of Pentium 1 builds and PSUs used to power them all don't give me much confidence.

I'm capable of refurbishing them, but as you said yourself, it may not be worth doing if it's a badly designed PSU. However, I don't have the know how to come to this conclusion just by looking at the insides. Weight test may be a good indication, as usually heavier equals better quality, but I'll need more than that. ;]

By the way, what do you guys do whan it comes to using modern PSUs in retro builds that lack molex/floppy connectors? Do you use adapters or do you desolder/cut everything unnecessary and replace them with molex?

I tend to treat all AT PSUs with a big dose of suspicion, even the ones that the seller claims to be working. They all get their voltages and caps checked and a decent visual inspection of internals before I let them near any of my AT stuff. I dont have the knowledge of how to repair them beyond changing caps but I do have a friend who is a sparky who does repairs for me but even he is wary of old AT stuff, the fabs did some seriously weird shit back in the day and even he is surprised by some of the designs implemented in old power supplies.

If you scrap any AT psus I could use some of the AT connectors.

But I say save them if they work.

Sphere478 wrote on 2022-07-26, 17:12:

If you scrap any AT psus I could use some of the AT connectors.

But I say save them if they work.

We cant save them all but even the dead ones can be salvaged for parts !

blackmasked wrote on 2022-07-26, 16:42:

I'm more concerned about AT PSUs to be honest, first 3 on that list. I do have a 486 and a couple of Pentium 1 builds and PSUs used to power them all don't give me much confidence.

I'm capable of refurbishing them, but as you said yourself, it may not be worth doing if it's a badly designed PSU. However, I don't have the know how to come to this conclusion just by looking at the insides. Weight test may be a good indication, as usually heavier equals better quality, but I'll need more than that. ;]

I see where you're coming from, I noticed there's a common concern in the retro scene with AT units in particular and I'm not sure where it came from. But there's this fear that these are inherently much more dangerous to your components than ATX. This is false, most of the instances of the power supply dying and taking components with it is due to bad design of the +5VSB line which is always on and can kill motherboard, memory and other stuff if it goes rogue. AT power supplies don't even have a standby line, so that's one major point of failure less vs. ATX.

If you're uncertain about those AT units being unable to handle a 486 or Pentium 1 then don't worry, they most certainly can. Those builds probably use around 50W of power at most (perhaps a bit more from the wall due to poor efficiency), so basically anything can power them. As I said, the design is usually very similar for all those AT PSUs, but if you want to know about specific things to look for: switching transistors in the primary, main transformer size, rectifier diodes and caps/inductors in the secondary. Those should be able to tell you whether the unit is under or over specced.

My take on these, for what it's worth: if those power supplies are currently working properly (meaning output voltages are stable and within range, no strange noises or burnt things) then with a recap + fan replacement if necessary then you should be just fine. But if you feel safer spending on a 500W Corsair or something like that then by all means go ahead, in my opinion that alternative is full of inconveniences vs. whatever benefits it can provide, but if it works for you that's what matters the most.

TheMobRules wrote on 2022-07-26, 17:21:

I see where you're coming from, I noticed there's a common concern in the retro scene with AT units in particular and I'm not su […]
Show full quote

blackmasked wrote on 2022-07-26, 16:42:

I'm more concerned about AT PSUs to be honest, first 3 on that list. I do have a 486 and a couple of Pentium 1 builds and PSUs used to power them all don't give me much confidence.

I'm capable of refurbishing them, but as you said yourself, it may not be worth doing if it's a badly designed PSU. However, I don't have the know how to come to this conclusion just by looking at the insides. Weight test may be a good indication, as usually heavier equals better quality, but I'll need more than that. ;]

I see where you're coming from, I noticed there's a common concern in the retro scene with AT units in particular and I'm not sure where it came from. But there's this fear that these are inherently much more dangerous to your components than ATX. This is false, most of the instances of the power supply dying and taking components with it is due to bad design of the +5VSB line which is always on and can kill motherboard, memory and other stuff if it goes rogue. AT power supplies don't even have a standby line, so that's one major point of failure less vs. ATX.

If you're uncertain about those AT units being unable to handle a 486 or Pentium 1 then don't worry, they most certainly can. Those builds probably use around 50W of power at most (perhaps a bit more from the wall due to poor efficiency), so basically anything can power them. As I said, the design is usually very similar for all those AT PSUs, but if you want to know about specific things to look for: switching transistors in the primary, main transformer size, rectifier diodes and caps/inductors in the secondary. Those should be able to tell you whether the unit is under or over specced.

My take on these, for what it's worth: if those power supplies are currently working properly (meaning output voltages are stable and within range, no strange noises or burnt things) then with a recap + fan replacement if necessary then you should be just fine. But if you feel safer spending on a 500W Corsair or something like that then by all means go ahead, in my opinion that alternative is full of inconveniences vs. whatever benefits it can provide, but if it works for you that's what matters the most.

My concern is with untested AT supplies, its mostly due to the age of the internal components than any other factor, so if they pass inspection and testing then as you say a re-cap and new fan and they are good for another 20 years.

Oh yeah, save old atx psus that have the -5v for sure

TrashPanda wrote on 2022-07-26, 17:26:

My concern is with untested AT supplies, its mostly due to the age of the internal components than any other factor, so if they pass inspection and testing then as you say a re-cap and new fan and they are good for another 20 years.

Yes, proper testing is a must, I use stuff like dead hard drives and motherboards as dummy loads for initial voltage checks. Regarding the components, if the unit works fine and there are no cracked components, burn marks or discoloration on the PCB it should be OK, under normal circumstances an AT rig doesn't put a lot of stress on them (especially compared with early '00s stuff).

blackmasked wrote on 2022-07-26, 16:42:

By the way, what do you guys do whan it comes to using modern PSUs in retro builds that lack molex/floppy connectors? Do you use adapters or do you desolder/cut everything unnecessary and replace them with molex?

I just use adapters. SATA -> floppy and Molex -> floppy connectors are probably fine even with questionable adapters due to the low power usage. SATA -> molex is iffy.

Sphere478 wrote on 2022-07-26, 17:41:

Oh yeah, save old atx psus that have the -5v for sure

^ What he said! ^

Older ATX power supplies with high current +5V and -5V present are the ones to keep alive.
Anything else, once it dies, replace it with the before-mentioned one.

But it may not be easy to find a lot of such ATX power supplies, so i also have most of my AT machines with their original PSUs. But once they die, i would be searching for ATX supply with the properties mentioned. On my "testbench" on the desk, i have 420W ATX supply just like described.

Heavy rated light weight PSU may be totally ok for light duty, if all components are in place. Most systems up to Pentium 3 regularly don't exceed 150W so keep an eye on the voltages. Like this 450W rated PSU I've got with rather tiny cooling fins. I just don't dare to hook it up to an Athlon XP system, but for a P3 it's working great.

It becomes more exciting when all kinds of components seem to be missing and placeholders are bridged with some piece of wire. Those I get rid of instantly.

If they are hissing then I give them away for free. There are people willing to pick them up in person. If nothing else at least they get a free fan.

TrashPanda wrote on 2022-07-26, 15:12:

blackmasked wrote on 2022-07-26, 14:48:

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important. […]
Show full quote

bofh.fromhell wrote on 2022-07-26, 14:31:

I'm certainly not an expert. But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-wast […]
Show full quote

I'm certainly not an expert.
But IMO any early ATX with standard pin-out and form factor PSU with less then 30A on +5v is e-waste.
Basically if you can easily replace it with a modern PSU don't bother =)

On a side note.
Wouldn't it, with all the expertise on this forum, be possible to design replacement guts for our failing AT and high amp +5v ATX power-supplies?
A new 300w'ish -modular- AT PSU with temp controlled fan? yes please!

I've had the impression that for Pentium 3 / 4 / early Athlon era it was +12V that was more important.

Anyway, I'd rather use a new PSU, but very few new power supplies have strong enough rails that are important for retro build and no molex / floppy cables.

In Pentium 1 / 2 builds that I have I ended up using more modern PSUs with 120mm fans that run nice and quiet, but again, lack of molex power cables is an issue and SATA-Molex adapters create a bit of a mess.

P4 wants a ton of +12v where as P3 and Athlon XP want as much +5v as you can give them, the higher end Barton's really do like +25Amps on the +5v rail but with a stripped down setup you can get away with less. (P3 is far more forgiving with +5v Amps as it doesnt draw anywhere as much power as a loaded Athlon XP system can, especially over clocked ones)

This is just my experience and I have a number of these systems, there have been others who have gotten Athlon XP to run just fine with modern ATX PSUs but I have no idea if they are running a lean setup that isn't hogging the +5v rail. I would guess that if they are running a setup with out Spinning Rust or Optical drives/Floppy Drives then the load on the +5v rail would be considerably less, a GPU with its own Power connector would also help a modern ATX PSU deliver the needed +5v Amps.

Athlon/Athlon XP are mainboard dependent on that regard. Some late Socket A boars (like my MSI KM3M-V) have the same type of 12V auxiliary CPU power connector as more modern systems have. Though with those late boards you have to give up on ISA.