Some ISA cards like Sound Blaster use the -5V.

The only PC motherboard that requires -5 is the first (max 64 kB integrated) IBM 5150 one 😀

And even then I don't know if it can be outright damaged by the lack of it (it's indeed a problem with RAM used, for example, in barely older S100 computers)

Hmm searched for "Green 500W" on ebay, not very impressed with the label and probably weighs about 1 pound and more than 10 still available. Maybe it was bad from the start ???
IMHO The only "Green 500w" PSU worth anything is the Antec Earthwatts EA-500D in green color, it weighs 3lbs + due to big primary tranny and very large heat sinks.....

I would chuck that "Green" PSU (the one from ebay) straight in the bin. That's a gutless wonder of a fire hazard just waiting to happen, even more so as they just stole the PSU design from Hercules PSUs (which are abysmal in quality.)

As @Horun pointed out, get an branded PSU - FSP, Delta, Newton Power, InWin Powerman, Seasonic, Thermaltake, Enermax and CWT's ISO PSUs are a few to name.

You can use a modern ATX power supply on an older AT board without any problems. This is what I do simply becasue AT power supplies are so old and unreliable and I don't want them taking out my "retro" hardware.

The -5 volts will only be a problem if you use one of the very few specific sound cards that uses it. If I recall, there are only a few, like the Sound Blaster 2 ISA. Please feel free to correct me if I am wrong, my memory isn't what it used to be, so I defiantly don't mind being told I'm misremembering, or just outright wrong. 😜

If you need the -5V for your ISA card, then you use a Voltage Blaster. They are readily available and affordable.

https://www.ebay.com/sch/i.html?_from=R40&_tr … Voltage+Blaster

There used to be an ATX to AT adapter harness that came with the -5v supplied in-line, but I can't seem to find them for sale anymore. They were identical to the one you see below, but they had the -5V added.

Here is a video I found from Phil's Computer Lab from many years ago reviewing one of them... I guess they are just not being made anymore.

https://www.youtube.com/watch?v=8QXmxdiNWIs

Plus, I suppose you can DIY one as well, it's not hard, but outside the scope of this thread and something I would only suggest if you knew what you were doing. 😜

Skalabala wrote on 2024-03-03, 13:33:

Hello everyone 😀

I bought a PSU from Ebay ''Green 500W''

Green, the famous power supply brand 😀 Did you buy it from US seller (California address)? https://www.ebay.com/itm/223855484253 ?
You will be happy to know its the exact same counterfeit/scrap as the one here AT power supply question

Looking for Green 500W on eBay... I'm not impressed. The PSU looks like the typical generic POS gutless wonder... and it goes for $25! WTF?! There's plenty of cheaper and better PSUs out there, especially 2nd hand.
The only thing that Green PSU would be good for is (de)soldering practice and (small) spare electrical components.

Skalabala wrote on 2024-03-03, 13:33:

Tested it on my P5A-B and it worked, tried it on Matsonic MS6260S and it died.
I installed post card and 5V is missing 🤣.

If it can power up a system, it's not exactly dead... though calling such gutless PSU as working wouldn't be correct either. 😁
So I'm curious what happened to it. Care to entertain us with some pictures or more details? 😀

StriderTR wrote on 2024-03-04, 01:26:

This is what I do simply becasue AT power supplies are so old and unreliable and I don't want them taking out my "retro" hardware.

If you consider ALL old PSU unreliable, you're missing out on some good hardware. There are quite a few good old units - some with all-Japanese caps too. Just have to know what to look for / which brand. ASTEC is one of these - I've seen nothing but solid PSUs with good quality Japanese caps from them. HiPro, Delta, and LiteOn are also excellent, though some of their units may or may not need a recap, depending on what era they were made in. I find most of them from the Pentium II era and older to have only or mostly Japanese capacitors and thus should be pretty bulletproof.

momaka wrote on 2024-03-04, 20:00:

Looking for Green 500W on eBay... I'm not impressed. The PSU looks like the typical generic POS gutless wonder... and it goes fo […]
Show full quote

Looking for Green 500W on eBay... I'm not impressed. The PSU looks like the typical generic POS gutless wonder... and it goes for $25! WTF?! There's plenty of cheaper and better PSUs out there, especially 2nd hand.
The only thing that Green PSU would be good for is (de)soldering practice and (small) spare electrical components.

Skalabala wrote on 2024-03-03, 13:33:

Tested it on my P5A-B and it worked, tried it on Matsonic MS6260S and it died.
I installed post card and 5V is missing 🤣.

If it can power up a system, it's not exactly dead... though calling such gutless PSU as working wouldn't be correct either. 😁
So I'm curious what happened to it. Care to entertain us with some pictures or more details? 😀

StriderTR wrote on 2024-03-04, 01:26:

This is what I do simply becasue AT power supplies are so old and unreliable and I don't want them taking out my "retro" hardware.

If you consider ALL old PSU unreliable, you're missing out on some good hardware. There are quite a few good old units - some with all-Japanese caps too. Just have to know what to look for / which brand. ASTEC is one of these - I've seen nothing but solid PSUs with good quality Japanese caps from them. HiPro, Delta, and LiteOn are also excellent, though some of their units may or may not need a recap, depending on what era they were made in. I find most of them from the Pentium II era and older to have only or mostly Japanese capacitors and thus should be pretty bulletproof.

That Green is nothing else but a rebranded Hercules of the lowest sub-garbage-tier (not even worth for spares, it's that bad) level. There's much better stuff out there - Enermax, Seasonic, ACBel Polytech, Bestec (not including the ATX-250-12E that is known to kill mainboards.), and heck, even CWT ISO (that actually read ISO on their label) aren't a option to discard IMO.

(btw I'm Dan81 from BCN 😀 )

rasz_pl wrote on 2024-03-04, 03:04:

Skalabala wrote on 2024-03-03, 13:33:

Hello everyone 😀

I bought a PSU from Ebay ''Green 500W''

Green, the famous power supply brand 😀 Did you buy it from US seller (California address)? https://www.ebay.com/itm/223855484253 ?
You will be happy to know its the exact same counterfeit/scrap as the one here AT power supply question

Yes its that, its junk for sure 😁

I used the PSU on the P5A-B overclocked t0 660MHz stable. Then I wanted to try the PSU on the MS6260s. I smelled something and it posted and froze in post.
Board never posted again and post card says 5V is missing 🙁
Should have gotten a better PSU since I am trying to have the fastest socket 7 in the world.

if you have a multimeter check for shorts / < 10 ohms on the AT connector. You may have have just blown a tantalum capacitor which are highly likely to blow. Look for the burnt part, check caps for shorts. Remove at least one side until the short is gone. If those check out then id move to the socket voltages i.e vcore. Feel around for hot chips is another simple method.
I also like to use pico power supplies for the older PC's i use, but its mainly for starting and running benchmarks. I went with a enermax for my main socket 7 and i use another for a socket A.

As a general policy, I suggest using a multimeter to measure the output of unknown power supplies before you plug parts you care about into them.
This won't show you the ripple, but that's a deeper thing to get into and requires expensive equipment. Checking the nominal voltages is easy and will weed out most dangerous PSUs.

A PSU needs a load before it will regulate properly, so for that you can plug in some junk hardware. Or you can rig up a dummy load using resistors, but they need to be beefy enough to handle the wattage that will be going through them.
After an initial measurement, let it run for a while, make sure the PSU still measures good after it's been working awhile and gotten hot. Then perhaps try an increased load, if you can provide one. If anything wants to die after 20 years of sleep, a heat cycle will help encourage that to happen before more valuable parts get involved.
After building a system, repeat the measurements to make sure the actual build is working well.
On boards that have BIOS voltage readings - ignore those and do your own measurements anyway. It's common for the onboard sensors to be inaccurate.

I have 3 AT PSUs. One I thought was good until I measured it, then I decided to set it aside. The 2nd was good enough to use, but not ideal (+5V is high and +12V is low, I tweaked a pot to compromise). The 3rd has basically perfect outputs.
It's a lot more assuring to have some measurements before you decide how much to trust a PSU, even if it's a good brand.

momaka wrote on 2024-03-04, 20:00:

If you consider ALL old PSU unreliable, you're missing out on some good hardware. There are quite a few good old units - some with all-Japanese caps too. Just have to know what to look for / which brand. ASTEC is one of these - I've seen nothing but solid PSUs with good quality Japanese caps from them. HiPro, Delta, and LiteOn are also excellent, though some of their units may or may not need a recap, depending on what era they were made in. I find most of them from the Pentium II era and older to have only or mostly Japanese capacitors and thus should be pretty bulletproof.

This is very true.

When I say unreliable, it's not just the quality of the component, but it's unknown usage and storage history. I'm the same way with most old/used electronics I buy. Sure, I can buy one from a brand I know was trustworthy, and if needed I can indeed repair it. However, when it comes to power supplies, I just don't see the point in taking that risk or having to do a repair when I can use a brand new modern PSU.

I'm also just not nostalgic about power supplies, I'm much more interested in the hardware itself, not what's powering it. 😜

Thought I would mention there are some psuedo generic older PSU that are OK. Some Enlight and ThermalTake models are ok. Not the greatest but a few models are very good....
Just need to research which ones.....

I had a look again and the test card says 3.3V is missing 😒 Using another power supply also.

Hmm so does it still say 5v is missing ? Have you looked at the bottom of the motherboard to see if any traces are burnt ?
Do you have a digi voltmeter or PSU tester and see what voltages are coming from the PSU's ?

Skalabala wrote on 2024-03-05, 02:08:

I used the PSU on the P5A-B overclocked t0 660MHz stable. Then I wanted to try the PSU on the MS6260s. I smelled something and it posted and froze in post.
Board never posted again and post card says 5V is missing 🙁
Should have gotten a better PSU since I am trying to have the fastest socket 7 in the world.

Again, you won't see the PSU run if the 5V is missing.

Even the most crude gutless wonders tend to (usually) shut down if a rail goes away (the few I saw that didn't, ended up in a cloud of smoke.)

So I'm more inclined to think that your POST card is likely just not making a proper connection in the PCI slot and thus not seeing the 5V rail.
I've actually ran into this same exact issue with my POST card on numerous machines - sometimes it's the 5V, sometimes it's some other PSU rail, and sometimes it's a stuck RESET... until I wiggle / re-seat the POST card in the slot. Then all of a sudden, all of these "missing" signals / rails were "fixed".

Skalabala wrote on 2024-03-08, 02:42:

I had a look again and the test card says 3.3V is missing 😒 Using another power supply also.

Yeah, probably your POST card being wonky at this point.
Or if this was on a different motherboard, maybe this one has 5V PCI slots only while the other had only 3.3V slots?

shamino wrote on 2024-03-05, 13:22:

As a general policy, I suggest using a multimeter to measure the output of unknown power supplies before you plug parts you care about into them.
This won't show you the ripple, but that's a deeper thing to get into and requires expensive equipment. Checking the nominal voltages is easy and will weed out most dangerous PSUs.

+1

Actually, a MM won't really show you *all* PSUs that are dangerous, but it could at least show you which ones might not be a good fit for the system.
I have several older group-regulated PSUs like this. These either don't like a heavy 5V load or a heavy 12V load, and one of them hates both, making it very hard to pair with any system. What's interesting is that some of these are actually half-decent to decent PSUs. But they just weren't designed for certain loads. The one that hates both 5V and 12V -heavy loads, for example (and older lower-end Sirtech HiPower platform) tends to squeal with a 12V -based system that doesn't put enough load on the 5V rail, and the voltages tend to be all over the place. It has a poorly designed compensation loop (which I will get to someday.) On the other hand, the same PSU is happy with a heavy 5V -based system... but then the 12V rail is sitting at 12.5 to 12.7V most of the time... which is very close to or out of spec. PSU voltages are stable, but I just don't feel comfortable feeding my HDDs and other hardware such a high 12V rail.

shamino wrote on 2024-03-05, 13:22:

A PSU needs a load before it will regulate properly, so for that you can plug in some junk hardware. Or you can rig up a dummy load using resistors, but they need to be beefy enough to handle the wattage that will be going through them.

+1 again.
Though instead of using power resistors as a dummy load, I suggest 12V incandescent or halogen bulbs. Should be pretty easy to find them in car/auto parts store or a hardware store that still carries MR16 12V bulbs for specialized lights (typically home lighting that uses a transformer.) A 20W incandescent or halogen will typically pull about 1A on the 5V rail and about 1.67 Amps from the 12V rail... so these are pretty good to use as dummy loads and won't require special cooling like a power resistor might.

shamino wrote on 2024-03-05, 13:22:

On boards that have BIOS voltage readings - ignore those and do your own measurements anyway. It's common for the onboard sensors to be inaccurate.

Like +10 for that one. 😁
I also never advise to trust BIOS voltage readings. Some can be accurate, but it's always worth double-checking.
The negative voltage rails are the ones most commonly mis-read by BIOS (not that these are of any importance, really.)

shamino wrote on 2024-03-05, 13:22:

It's a lot more assuring to have some measurements before you decide how much to trust a PSU, even if it's a good brand.

If it's a good brand PSUs and built well inside, I will always trust it.
But again, it just comes down to: is the PSU a good match for the system you're trying to run?
With group-regulated PSUs, it's not always obvious until you do some measurements, like you said.

StriderTR wrote on 2024-03-05, 18:36:

However, when it comes to power supplies, I just don't see the point in taking that risk or having to do a repair when I can use a brand new modern PSU.

The thing is, some older PSUs can be really bullet-proof, especially with new quality Japanese caps (if they didn't come with those already.) They will continue to work many years after most modern (APFC) PSUs have blown their primary caps. While I don't condone APFC, it's a circuit that puts extra strain on the primary cap(s) in the PSU and therefore they will have a much shorter life compared to non-PFC or PPFC PSUs that run their primary caps at line frequency only.

Skalabala wrote on 2024-03-08, 02:42:

I had a look again and the test card says 3.3V is missing 😒 Using another power supply also.

Yeah, probably your POST card being wonky at this point.
Or if this was on a different motherboard, maybe this one has 5V PCI slots only while the other had only 3.3V slots?

PcBytes wrote on 2024-03-04, 20:19:

(btw I'm Dan81 from BCN 😀 )

Hey hey! 😀
Yeah, I figured this I think a few years back when I came across some posts on Vogons (I think it was a rig/PSU that you had posted on BCN too, so I made the connection pretty quickly.) I see some other BCN members here too, which is pretty cool.

Horun wrote on 2024-03-08, 03:02:

Hmm so does it still say 5v is missing ? Have you looked at the bottom of the motherboard to see if any traces are burnt ?
Do you have a digi voltmeter or PSU tester and see what voltages are coming from the PSU's ?

I am sure both PSUs work. 5V is working. Did not do a good inspection yet. Will give it a go with multimeter sometime.