AT Power Switch on ATX Computer

[mudpark41]

I have an old case that I built a music server into. I cannot get the case to start anymore. It is an AT standard case so It has the long black wire thing from the PSU cut off. I Had this thing running an ATX standard comp for a while but then I remove the wires I had running from the black cable. Now I forgot which wires are used to make the power switch work.

I HAD the power buttons hooked up to the AT wire to turn on the power supply. I cut the black wire and stripped the little wires inside the large black rubber insulation. Now I can remember which of the smaller wires are used to turn the computer on. Anyone know what I need to do?

Click for Good Res Picture of what I am talking about
http://www.quitethegamer.com/staff/matt/Wires.jpg

[craig588]

Take a multimeter and find out which pair of wires acts as a momentary switch.

Alternativly you can get momentary switches for something like 1$, probably less.

[mudpark41]

More fun to try and figure out the challenge of these wires. I have had the working before. If I can just remember which Wire I hooked them up to.

[Thorry]

Dude that's really dangerous!!!

READ THIS ENTIRE POST AND DO NOT PLUG IN THE PSU, YOU WILL DAMAGE YOUR HARDWARE AND PROLLY KILL YOURSELF...

On those old AT power switches they didn't use a simple connect signal like on the ATX power cables, they actually disconnected the AC mains...

The brown wire needs to be connected to the black wire and the blue to the white, however you need to be VERY carefull. If you have had this PSU connected to the mains you are lucky you didn't electrocute yourself.

The brown and blue ware are the mains, they have 230 or 115 volts on them (depending on where you live). The black and white cable connect to the PSU, you need to connect the mains to the PSU.

You are crazy if you want to connect this to the mobo, it will blow the thing up.

Why did you remove the switch that was on there? If you wanted to mod it, put it back. If you want the PSU to be always on you can simply remove the entire switching wire and solder the mains to the PSU inside the PSU at the connector, this is much safer. Otherwise solder them together and use good wire insulation.

Also a AT PSU on a ATX motherboard won't work as the AT PSUs don't provide a 3.3 volt line. You can get this from the 5 volt line, but it isn't worth the effort as like for 10 dollars you can get a perfect ATX PSU.

[craig588]

That's not what he's doing at all, and what you're proposing wouldn't be that dangerous if someone did it right.

He just needs to get the momentary switching action from the AT switch. I already told him how to do it, use a multimeter and check which pair acts as one.

AT PSUs do have 3.3 lines. In theory if you found a good one there's no reason it shouldn't work on a ATX mobo, there is no difference in on 12V line or another 12V line. Just make sure it's a good PSU because most AT PSUs were weak and not very clean because the power demands of P1s with no videocards are practially nothing.

[BugsBMD]

Is that wire comming from the swich like in this picture? If so the swich should have a pictrure on the side of it imprinted on the plastic that shows what wires are conected when you push or flip the swich. I hope this helps.

[Thorry]

That's not what he's doing at all, and what you're proposing wouldn't be that dangerous if someone did it right.

He just needs to get the momentary switching action from the AT switch. I already told him how to do it, use a multimeter and check which pair acts as one.

AT PSUs do have 3.3 lines. In theory if you found a good one there's no reason it shouldn't work on a ATX mobo, there is no difference in on 12V line or another 12V line. Just make sure it's a good PSU because most AT PSUs were weak and not very clean because the power demands of P1s with no videocards are practially nothing.

1 - That's not what he is trying to do: He is asking which of the smaller wires inside the big black wire to connect to turn the PC on.

2 - You do not need a momentary switch, you need a big 230 volts, 8 amps AC switch.

3 - Those small wires inside the big black cable connect to mains, so it is dangerous!

4 - AT power supplies do not have a 3.3 volt line. Voltages on a AT power supply are: 5, 12, -5 and -12. There is no 3.3 volt line. See pinout: http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=pinconmth_at_power

5 - Nothing is dangerous if done right... :X

[craig588]

4. I was thinking of Dell for a minute, nevermind about that.


Look at his photo, he's trying to connect it to the mobo header. He's not talking about the mains.

[Thorry]

That big black cable holds mains.

On old AT systems there was a big black cable with a switch on the end (to be connected to the power button at the front of the case). The switch there was a big switch that actually connected mains to the PSU.

The blue cable is the neutral and the brown is the phase, the black and white are connected to the PSU. You need to connect the blue to the white and the brown to the black to start the PSU (it just starts as soon as it's got power).

Because these wires are mains you need a big switch, protected against sparks and that's why the big wire has so much insulation around it. If it were signal wires they wouldn't have such insulation and would look like the other cables on the photo.

If you connect the motherboard to the cables coming out of the big black wire you would have some nice fireworks and possibile kill yourself.

My advise:

Just go out and buy a ATX PSU, it isn't worth the effort fooling around with old AT PSUs.

If you need the ATX motherboard to power on as soon as it gets power you can connect a 16v 200 uF cap to the power-on pins on the motherboard. This will cause the motherboard to short the cap turning the system on and then load the cap causing it to block current.

[craig588]

Just because the switch used to switch the mains doesn't mean it has to or does anymore. It's not going to have voltage in it just because it was designed for the mains. If I was there I would grab those wires without fear. There's no voltage in them. They are just wires out of a switch.

Should I cut up one of my AT PSUs and present a similar picture with me holding onto the wires from the switch?

He already has an ATX psu, he just needs to use the AT switch to act as a momentary switch to trigger the mobo. He doesn't need another one.

[[XC] Lead Head]

Here is a pic on how to wire it up,

you could also use the white and black wires, your choice

[nn_step]

Here is an idea buy A NEW ATX case for $25 and not risk your hardware...

[1031.nu]

Just because the switch used to switch the mains doesn't mean it has to or does anymore. It's not going to have voltage in it just because it was designed for the mains. If I was there I would grab those wires without fear. There's no voltage in them. They are just wires out of a switch.

Should I cut up one of my AT PSUs and present a similar picture with me holding onto the wires from the switch?

He already has an ATX psu, he just needs to use the AT switch to act as a momentary switch to trigger the mobo. He doesn't need another one.

The old AT switches arent momentary, they always stayed charge when the computer was on, if I remember correctly. So if he were to push the button to turn it on, the switch would remain closed until he pushed it again to reopen and it disconnect the connection.

Bets choice to me seems to just buy a new switch at Radio Shack for no more than 3 dollars, but you most likely will need to drill your case for a clean install (which isn't that bad).

[Ugly n Grey]

Just turn it on/off to power on then on/off to turn it off. Then it's a momentary switch... geez

[BugsBMD]

Yeah you can do that or if you want to you can take the switch apart and remove the piece that holds the button in and then it becomes a simple push button switch. I have done this many times and it works very well you just have to be careful doing it.

[1031.nu]

Just turn it on/off to power on then on/off to turn it off. Then it's a momentary switch... geez

That would get annoying after awhile, 4 times to turn your computer on and off.


Yeah you can do that or if you want to you can take the switch apart and remove the piece that holds the button in and then it becomes a simple push button switch. I have done this many times and it works very well you just have to be careful doing it.

I like his idea better.

[Ugly n Grey]

depends if it's a spring loaded button type or a rocker switch type..

I can see how all that button pushing would become exhausting.... might have to hit the gym

[1031.nu]

depends if it's a spring loaded button type or a rocker switch type..

I can see how all that button pushing would become exhausting.... might have to hit the gym

Just a note about the gym ... since ATX motherboards became standard the gym has removed all of there AT Power Button Pushing Benches ... :( . If it’s a rocker switch you can place a tiny spring underneath the switch so that it always pushes back to the open position. With that much work again .. Buying a new switch would be easier. Also less strain on your fingers.