Try manually connecting the green and black wires together (using a paperclip or something similar) and see if the power supply turns on. It's possible the switch is broken, or you haven't connected the leads properly to form a connection.

It's also worth mentioning that the AT standard requires a -5V rail on pin 9, whereas this is optional on the ATX standard; check to make sure you have a white lead on pin 20 of your ATX unit. If you don't, it probably will not work.

AT and ATX standards are universal and convert power into the same DC voltages on the output, so you do not need to worry about differences in mains power.

Snover wrote:

Try manually connecting the green and black wires together (using a paperclip or something similar) and see if the power supply turns on. It's possible the switch is broken, or you haven't connected the leads properly to form a connection.

It's also worth mentioning that the AT standard requires a -5V rail on pin 9, whereas this is optional on the ATX standard; check to make sure you have a white lead on pin 20 of your ATX unit. If you don't, it probably will not work.

AT and ATX standards are universal and convert power into the same DC voltages on the output, so you do not need to worry about differences in mains power.

Drat, I know there's no -5V rail on my ATX PSU. There's no white lead either. 🙁

I always wanted to get a new PSU working with an old PC, so I guess I need to see if any online retailers here in the UK sell ATX PSUs which still have the -5V rail.

Thanks for the very useful info! 😀

It is extremely unlikely that you will find any manufacturer still selling new power supplies with the -5V rail since it has not been part of the ATX spec for quite some time. It looks like Sparkle (SPI) might still have -5V rails on their “low-end” units, but the photos I'm looking at could be outdated. Good hunting!

There is a not too complicated cirquit that makes -5V from -12V. Two capacitors and a 7905 voltage regulator. The power supply should power up also if there is no -5V.

Could you make a close up photo of the connector block from both sides?

I had a browse on ebay, and found this PSU item -

110342165169 (copy-and-paste in to ebay's search box)

The seller's listing states:

* Max Outputs:
+12V (24A)
-5V (0.5A)
3.3V (28A)
-12V (0.8A)
-5V (35A)

Promising? I don't know why -5V is listed twice. Maybe the last one is supposed to be +5V? But the 0.5A for the first -5V listing looks interesting. Is 0.5A roughly the figure I'm looking for?

It's cheap too. 🤑 Maybe it's worth a shot? 😀

PS - sadly however, I can't clearly see any white cable in that tiny photo of the 20-24 pin power cable... 😒

Unless you want your computer to explode, do not ever buy a non-name-brand power supply, ever. Especially not from eBay.

all my old pc's have PSU's that are from unknown companies. Some don't even have a brand. but they still work 🤣

all my old pc's have PSU's that are from unknown companies. Some don't even have a brand. but they still work Laughing Out Loud

Because old PCs only need like 30-50 Watts so the 200W power supplies are overdimensioned and can handle it even if they are really only able to supply 100W. This is more a problem of modern PCs as those need lot's of juice.

h-a-l-9000 wrote:

There is a not too complicated cirquit that makes -5V from -12V. Two capacitors and a 7905 voltage regulator.

I'm afraid that's beyond my current capabilities ATM.

h-a-l-9000 wrote:

The power supply should power up also if there is no -5V.
Could you make a close up photo of the connector block from both sides?

Very unfortunately, the camera I have has no macro ability. Anything closer than about 18cm, and the image goes very blurry. However, I'm happy to describe any detail you need. When you say "connector block", do you mean the white plastic rectangular block at the end of the AT cable converter gadget, in the centre top of the screen? Thanks.

The photo below shows another similar gadget. This one has no switch on the end of the green & black cables, but does have a 3rd white mobo connector, with 3 orange and 3 black cables. (I'm guessing that I don't need to use this 3rd connector.)

But I could try using this gadget instead of the other one which has the on/off power switch. I could use a paperclip or something similar to link the green and black cable ends together. Shall I try that? (Just to see if I get any power at all.)

I could use a paperclip or something similar to link the green and black cable ends together. Shall I try that? (Just to see if I get any power at all.)

You can try that to exclude the switch being the problem.
Did you disconnect the drives in the case? It might cause probelms if a drive gets power but the mainboard it is connected to does not.

On your first photo, I hope there is an empty gap between yellow and orange and the red wire goes to the lower row. If it is between yellow and orange that would be a mistake.
The -5V may be whatever color on your ATX power supply, only if the spot opposing the white cable of your adapter is empty then it has no -5V.

The third black/orange connector on your second photo suplies the 3.3V to a special mainboard (Packard Bell, HP, Compaq or somesuch I think I've seen it on) and isn't needed for a normal AT. Also notice blue and white are switched on that one.

h-a-l-9000 wrote:

Did you disconnect the drives in the case? It might cause probelms if a drive gets power but the mainboard it is connected to does not.

The drives in the case were disconnected.

h-a-l-9000 wrote:

On your first photo, I hope there is an empty gap between yellow and orange and the red wire goes to the lower row.

Yes, all is OK. 😀

h-a-l-9000 wrote:

The -5V may be whatever color on your ATX power supply, only if the spot opposing the white cable of your adapter is empty then it has no -5V.

Drat. The 'opposite spot' is indeed missing. 🙁

Snover wrote:

It is extremely unlikely that you will find any manufacturer still selling new power supplies with the -5V rail since it has not been part of the ATX spec for quite some time.

It's difficult, but not impossible. In the German "Saturn" there is a PSU of 450W-650W that has a -5V rail but unfortunately I forgot the manufacturers name. The reason lies in the fact that I didn't buy it - it was really expensive: about 60-80e. So I just bought a second hand Levicom 450W for 15e.

I have the exact same converters... 😀
(both versions!)
I bought some xtra switches separately.
(I assume you have connected the black/green cable correctly to the switch?)

- Works just dandy on my socket3 pentium board, with the Aopen PSU mentioned below.
(though I STILL can't get it to find my hdd... <sob> )

As for AT compatible PSU, here's one I bought this week (£40, too expensive?) that actually has a -5v line:
http://www.novatech.co.uk/novatech/specpage.html?NEX-PSUS35

And, it also says it has 220 max on the +5v and +3.3v volt lines, which is important for older computers. Check section 1.5 in wiki:
http://en.wikipedia.org/wiki/Atx

Another 'fun' link:
http://www.playtool.com/pages/psucompat/compat.html
http://www.playtool.com/pages/psuconnectors/connectors.html

Haven't tested it yet though, and no info in that shop page... but the connector is filled up/no missing contacts, and it says so on the box(!) - so I take it it should be correct.

Though, not sure how the 400w version is wired.
(available from same site, +50w at £18 xtra, hmm...)

AND, the 2 big capacitators inside state the once dreaded 'TEAPO'.... you're hereby warned. Though I have the impression the reputation has bettered later years.
(I looked at my 11(!) year old Aopen/FSP-235(FortronSource?) 235w PSU, which is still working, and it has 2 Rubycon ones...)

.

elfuego wrote:

Snover wrote:

It is extremely unlikely that you will find any manufacturer still selling new power supplies with the -5V rail since it has not been part of the ATX spec for quite some time.

It's difficult, but not impossible. In the German "Saturn" there is a PSU of 450W-650W that has a -5V rail but unfortunately I forgot the manufacturers name. The reason lies in the fact that I didn't buy it - it was really expensive: about 60-80e. So I just bought a second hand Levicom 450W for 15e.

Hmmm...you got me interested! I'm really keen on buying a good quality ATX PSU, with a -5V rail. What is this German Saturn you speak of? Is it a website, a or PC magazine perhaps?

Please wrack your brains over the weekend...maybe you'll remember the manufacturer's name! 😀 Thanks a lot! 😀

PS - is it OK to run a German PSU in the UK? I know the power plugs are different - I think you have 2 pins, and we have 3. Maybe there's a switch on the back of the PSU that makes it "UK power supply friendly", for want of a much better phrase.

bestemor wrote:

I have the exact same converters... :) (both versions!) I bought some xtra switches separately. (I assume you have connected the […]
Show full quote

I have the exact same converters... 😀
(both versions!)
I bought some xtra switches separately.
(I assume you have connected the black/green cable correctly to the switch?)

- Works just dandy on my socket3 pentium board, with the Aopen PSU mentioned below.
(though I STILL can't get it to find my hdd... <sob> )

As for AT compatible PSU, here's one I bought this week (£40, too expensive?) that actually has a -5v line:
http://www.novatech.co.uk/novatech/specpage.html?NEX-PSUS35

And, it also says it has 220 max on the +5v and +3.3v volt lines, which is important for older computers. Check section 1.5 in wiki:
http://en.wikipedia.org/wiki/Atx

Another 'fun' link:
http://www.playtool.com/pages/psucompat/compat.html
http://www.playtool.com/pages/psuconnectors/connectors.html

Haven't tested it yet though, and no info in that shop page... but the connector is filled up/no missing contacts, and it says so on the box(!) - so I take it it should be correct.

Though, not sure how the 400w version is wired.
(available from same site, +50w at £18 xtra, hmm...)

AND, the 2 big capacitators inside state the once dreaded 'TEAPO'.... you're hereby warned. Though I have the impression the reputation has bettered later years.
(I looked at my 11(!) year old Aopen/FSP-235(FortronSource?) 235w PSU, which is still working, and it has 2 Rubycon ones...)

.

Whoa! 😎 Bestemor, please would you be kind and keep us posted about this PSU, when you test it? If it works (with the ATX to AT converter), then I will definitely get one too. This is just what I'm after - a good quality & quiet PSU, with a -5V rail.

Thanks a lot! 😁

Ok, since you ask so nicely 😎

Just tested(using the 3-pronged converter version, P8/9/10), and boots with no other problems than the one's mentiond for the Apoen PSU.

Granted, I have no idea if this mobo NEEDS -5v, but it is a late 1994 Pentium1 model (SiS chipset, only PCI and ISA).
AND, I have not tested anything past POST, i.e. ISA soundcard etc, but it finds the floppy on the ISA floppy controller, so... who knows ?

Your choice...

BTW, that ebay one you quoted id number for, looks very similar to this one:
http://www.novatech.co.uk/novatech/specpage.html?NEX-PSUS30

And at £13ish inc shipping(NEW item?), no harm in trying, or ? 😅

.
***

PS: I should probably mention that my model number is "NX-3500"(written on the PSU casing label), as opposed to the "NEX-PSUS35" mentioned at the novatech site ??

So, I strongly suggest you ASK them (phone/email) for the actual specifics - but as it will be written on the retailbox if there is a -5v line, I assume they would have little problem confirming whether it has one or not... (?)

.

PPS: just noticed, that they refer to it as "NX-3500" in the 'overview' text/blurb below the picture, which could indicate it is indeed the same model as mine, but you never know...

.

Thanks very much for your post! 😀

I just checked out this website -

http://www.nexustek.nl/NXS-nx3500realsilentpo … pply350watt.htm

It's from nexustek. Scroll down a bit, then you will see:

Power Characteristics

There, you see -5V rail information.

Also, I scroll back to the top of this page, then click on the "Where to buy" link. Lo and behold, it lists Novatech as a reseller.

Looks like I'm in luck! Thanks a lot!! 😁

I looked at that page of yours, but I still feel the need to warn you - as the model in question there is the NX-3500, which of course has the -5v line... was never any doubt about that.

The NEX-PSUS35 on the other hand... still not convinced.
BUT, it could of course just be some naming confusion/webshop choice, and the 2 model numbers really are the same one...

Anyway, good luck ! 😁

bestemor wrote:

I looked at that page of yours, but I still feel the need to warn you - as the model in question there is the NX-3500, which of […]
Show full quote

I looked at that page of yours, but I still feel the need to warn you - as the model in question there is the NX-3500, which of course has the -5v line... was never any doubt about that.

The NEX-PSUS35 on the other hand... still not convinced.
BUT, it could of course just be some naming confusion/webshop choice, and the 2 model numbers really are the same one...

Anyway, good luck ! 😁

I understand 100% now. What I'll do is contact nexustek themselves in the Netherlands, and ask them if the NEX-PSUS35 is simply a "renamed UK label" for the NX-3500. I have a feeling that it is, but I'll fire off an email to them before I buy the NEX-PSUS35 from Novatech. 😀