Like the title says, I was wondering if anyone here can tell me how to turn on an AT PSU without a mobo attached so I can check it for voltages with a multimeter? Also if you have any insight into how to check and what to look for I would greatly appreciate it. Thank you! Oh and looking inside, the caps and stuff loom alright to me.
Edited to add a sentence.
You'll need to provide a minimum load, else it won't start or the voltages will be all over the place. I keep a couple of dead HDDs (that are still spinning) for this purpose. The voltages might still be a bit off with such a light load, but at least you'll know if it's safe to use it to power a full system before a final voltage check.
Thanks I have a couple I can attach. Do you know what wires to jump to start it? I cant find info on Google it just shows ATX
Assuming yours is the type with the power switch on a thick black cable, it will turn on immediately when you press it.
jakethompson1 wrote on 2020-08-24, 01:40:Assuming yours is the type with the power switch on a thick black cable, it will turn on immediately when you press it.
Okay. Yeah mine has a thick black cable that goes to the front of the case to a big switch. Thanks so much. I have to work for the next few days, but when I get it tested I will be sure to get on and update everyone on how it's doing. I'm really hoping it runs well so I can get am authentic dos early 90s experience. Nothing wrong with dosbox, it really works well, but I never got the real experience back in the day. Too poor 🤷🏼♂️
Mephusto wrote on 2020-08-24, 01:51:Okay. Yeah mine has a thick black cable that goes to the front of the case to a big switch. Thanks so much. I have to work for the next few days, but when I get it tested I will be sure to get on and update everyone on how it's doing. I'm really hoping it runs well so I can get am authentic dos early 90s experience. Nothing wrong with dosbox, it really works well, but I never got the real experience back in the day. Too poor 🤷🏼♂️
Careful with AT PSUs as that cord to the front carries mains voltage.
All hail the Great Capacitor Brand Finder
gdjacobs wrote on 2020-08-25, 06:15:Careful with AT PSUs as that cord to the front carries mains voltage.
I'll second this too.
Off at the wall, power cable unplugged both ends.
Turn PSU switch on. Move it somewhere safe.
Plug power cable into PSU, then wall.
Turn on at wall.
At least, that's what I'm trying to always do, even for the fully heatshrinked switches. I've been zapped a couple of times and that was when being careful too.
The only way, if you have to do it at all, is to not touch that switch when the PSU is plugged in.
It don't mean a thing if it ain't got 5-pin DIN.
Roland addict and founding member of the Association Of Molex Haters
There do exist AT PSUs with a power switch on the back instead of cords that carry to the front. Why this is, I don't know. But I have one and use it myself to test motherboards with AT power connectors.
(Decommissioned:)
mockingbird wrote on 2020-08-25, 14:23:There do exist AT PSUs with a power switch on the back instead of cords that carry to the front. Why this is, I don't know. But I have one and use it myself to test motherboards with AT power connectors.
Early generation machines. Front power switches are way more convenient, so they quickly became the standard.
All hail the Great Capacitor Brand Finder
gdjacobs wrote on 2020-08-25, 06:15:Careful with AT PSUs as that cord to the front carries mains voltage.
Thanks so much! I didn't know that and I probably would have gotten zapped. I never would have thought they'd have mains voltage on them. I'm off the next 2 days and I am planning on working on testing them out
Mephusto wrote on 2020-08-26, 04:46:gdjacobs wrote on 2020-08-25, 06:15:Careful with AT PSUs as that cord to the front carries mains voltage.
Thanks so much! I didn't know that and I probably would have gotten zapped. I never would have thought they'd have mains voltage on them. I'm off the next 2 days and I am planning on working on testing them out
Use insulating tape on the wire contacts to avoid accidental touching.
Yeah I will. I usually dont mess around anything that is still connected to an outlet or with large capacitors. Electricity is very respected by me.....I'm scared of it.
Mephusto wrote on 2020-08-26, 05:52:Yeah I will. I usually dont mess around anything that is still connected to an outlet or with large capacitors. Electricity is very respected by me.....I'm scared of it.
You can also bypass the PSU rocker switch with a single switch adapter, that way you don't have to touch the PSU at all. Just switch it on and use the adapter's switch to turn it on/off.
Miphee wrote on 2020-08-26, 06:13:Mephusto wrote on 2020-08-26, 05:52:Yeah I will. I usually dont mess around anything that is still connected to an outlet or with large capacitors. Electricity is very respected by me.....I'm scared of it.
You can also bypass the PSU rocker switch with a single switch adapter, that way you don't have to touch the PSU at all. Just switch it on and use the adapter's switch to turn it on/off.
well thats cool I didn't think of looking for something like that. Are the old AT power supply switches that bad?
Mephusto wrote on 2020-08-26, 13:58:well thats cool I didn't think of looking for something like that. Are the old AT power supply switches that bad?
Not at all but it's unsafe when it's outside the PC case.
The bare contacts are often visible, the cable lugs may become loose so you have a chance to accidentally touch them and get electrocuted.
So you either use insulating tape to cover the contacts or use a separate switch and don't touch the PSU at all.
quicknick wrote on 2020-08-24, 01:15:You'll need to provide a minimum load, else it won't start or the voltages will be all over the place. I keep a couple of dead HDDs (that are still spinning) for this purpose. The voltages might still be a bit off with such a light load, but at least you'll know if it's safe to use it to power a full system before a final voltage check.
This is something I have toyed with for actually building an AT power tester. 50-100W resistors are cheap. What sort of loads would be required on each rail for a decent power tester? Do you just gun it at max power output as this should be specified on the PSU somewhere? Do you use high resistances to measure the voltage accurately, but that gives low load? Obviously overloading with low resistances is a bad idea as once the magic smoke gets out, you can't put it back in...
I've noticed that sometimes AT PSU power buttons have four wires, sometimes two. Isn't a two-wire switch rather unsafe as, depending on how the user's outlet might be wired, it could only be switching neutral?
I don't recall ever having seen one that only has two, got an example for that?
if it does it probably has some internal startup circuit.
imi wrote on 2020-08-26, 18:12:I don't recall ever having seen one that only has two, got an example for that?
if it does it probably has some internal startup circuit.
The one I posted is a converter cable from China, haven't seen a single-pole switch on a regular PSU either.
Ah yes it seems the two-wire ones I've seen actually had an ATX converter hooked up, whoops.
