Computer power supply question

[Pacu]

Do i need to have the power supply plugged into the motherboard for the power supply to come on? I plugged in my power supply this morning to test out one of my LED fans and nothing. This is my second PS and i wanted to test it out before i installed everything. It's an Antec 500w Earth series.

So far i have plugged it it, turned it on and the fan doesn't spin -no power to the fan when i connected it.

i think i'm missing something.

[Mike]

If the fan/leds/etc are plugged into the motherboard and is getting power through it then I would think you'd have to plug the power supply into the motherboard. But to simply turn on the power supply, you should be able to simply plug it and have it power up, even if it's not plugged into the motherboard.


Mike

[Pacu]

the fan/power cord are on a different set of cords not connected to the motherboard. They should connect and power up without the 20/24 pin connection to the motherboard i think.

[Mike]

Hmmm, maybe not. You might need a multi-meter to check and see if the pins are hot and at what voltages they are at. At one time Dell used to have a weird pin out on their power supplies. In fact, you couldn't use an off the shelf power supply for your Dell if it crapped out on you, you had to buy one from them. For that, you got appropriately gouged.

Not saying this is the case, but you should check it out with a multi-meter to make sure the are at least getting power.

Mike

[Neil]

the fan/power cord are on a different set of cords not connected to the motherboard. They should connect and power up without the 20/24 pin connection to the motherboard i think.

Most modern supplies will not power up without an active load.  You're going to have to run your testing once its all built

You can buy simple PSU testers for a few pounds/dollars but unless you're going to be doing this day in and day out I wouldn't bother.

[Pacu]

i just got it tested and it works fine. So it does indeed need to be connected up properly to turn on. Thanks for the help people

[Grant Lamontagne]

Yes, it's funny how often electronics work better simply by plugging them in!

Def

[MTguy]

Yeah, most of them need to be plugged in...but there is away around it, you can short out two pins on the connector for the motherboard...I dont remember what pins, i saw it on a website...It worked for me...I use to use an old power supply to power a car radio in my garage...just plug in the power supply and it converts 120ac to 12vdc.

[Pacu]

after even further research ..the motherboard sends a signal to the power supply to turn on.

so far on my newbie computer building errors

power supply questions
buying the wrong size fans...i bought 80mm when i needed 120mm

it's all a learning process

[RTAdams89]

If you are using an ATX (or any of the variants) then there is no way to turn on the power supply without having it connected to a motherboard (or tester). Unlike the old AT style power supplies which had two wires (carrying 120 volts!) running to a switch mounted on the computer tower, the new power supplies don't have any wires that carry more than 12 volts DC. In the 20/24 pin harness is a pin (pin #14, usually green) that carries a small voltage/current. When that pin is shorted to ground, the power supply "turns on" and provides it's usually assortment of 3.3/5/12 voltages on the appropriate wires. You will find some ATX power supplies with a rocker which built into them. This usually breaks the 120v AC coming into the power supply to completely kill it, as without that switch, the power supply is always "on" to some degree to be waiting for the motherboard to tell it to turn on.

PS, Dell and Sony have had periods where their OEM power supplies/motherboards used retarded, non-standard pinouts. So, if you are ever working on an older Dell or Sony, make sure you verify the pin outs are correct before swapping power supplies or motherboards with non-OEM direct replacements.

[Pacu]

that's some good info there RTAdams89 

wonder why they don't include that useful tidbit of info in the user manual?  Guess they figure one should know that already.

[WhichDawg]

buying the wrong size fans...i bought 80mm when i needed 120mm

eeep! what kind did you get? I got this and luv it! http://www.newegg.com/Product/Product.aspx?Item=N82E16835608010
(read the reviews)

[Pacu]

antec tricools     it's ok though    i took the 80mm and retrofitted it into my current rig with my yates fans

[Neil]

If you are using an ATX (or any of the variants) then there is no way to turn on the power supply without having it connected to a motherboard (or tester). Unlike the old AT style power supplies which had two wires (carrying 120 volts!) running to a switch mounted on the computer tower, the new power supplies don't have any wires that carry more than 12 volts DC. In the 20/24 pin harness is a pin (pin #14, usually green) that carries a small voltage/current. When that pin is shorted to ground, the power supply "turns on" and provides it's usually assortment of 3.3/5/12 voltages on the appropriate wires. You will find some ATX power supplies with a rocker which built into them. This usually breaks the 120v AC coming into the power supply to completely kill it, as without that switch, the power supply is always "on" to some degree to be waiting for the motherboard to tell it to turn on.

PS, Dell and Sony have had periods where their OEM power supplies/motherboards used retarded, non-standard pinouts. So, if you are ever working on an older Dell or Sony, make sure you verify the pin outs are correct before swapping power supplies or motherboards with non-OEM direct replacements.

Just add to this for anyone else reading, the paperclip trick for testing ATX supplies isn't foolproof as some PSUs will not power up without a load.  The PSU testers have a huge honking great resistor in them to provide a dummy load as well as a switch to trick the PSU.   I don't know about the Sony supplies but (back in the day) we found that to use standard supplies in Dells was doable by rearranging the ATX plug to Dell's unique arrangement.  What the heck were Dell thinking    Of course that was assuming the PSU wasn't physically non-standard as well

Bad luck on the fans but at least you were able to reuse them

[Magnus]

every power supply I have ever tested works fine by shorting the green wire to any black one (all black wires are ground).

[Whoey]

there is a way to get a PSU to fire-up without a motherboard but involves jumping two pins on the motherboard connector to fool it into thinking there is a motherboard installed.

http://aphnetworks.com/lounge/turn_on_psu_without_motherboard_the_paperclip_trick

Should work, but probably better to wait for a mainboard, or use an old one...