I bought a brand new atx power supply (400w) and i was going to make sure it worked before i stuck it in a computer so I connected the cord to it and plugged it in and the fans won't come on. Now I've tested other power supply's out like this and their fans have came on. Does it need to be connected to the motherboard for some reason or is it just dead? btw, its a switching power supply (whatever that is) thanks.

Yes it needs to be connected to the mobo. You could cross two wires on the connector, but I wont tell which two as that would not be consistent with my training and experience. It will work, just install it

Zo

*EDIT*

Why the computer/fan does not turn on after I flipped the power switch to ON located on the ATX power supply?
ATX power supply is different from AT power supply. It depends a logic circuit on the motherboard to turn it on. Once you flipped the power switch on the ATX power supply to on (some ATX power supplies do not even have such a switch), the ATX power supply sends a 5V 720MA current to the motherboard through pin 9 on the power connector. That current is for WOL (Wake-up On Lan) and power on circuits. There is a power-on jumper on the motherboard that connects to the pushbutton located in front of ATX case. When the pushbutton is pressed, it sends a signal to the mothboard, which in turn notifies the ATX power supply to turn on the full power. The location of the power-on jumper on the motherboard is manufacture dependent. You will need to read your motherboard manual to locate that jumper. At any event, do not try to manually jump-start the power supply without attaching motherboard. Since the power supply is expecting certain sensing circuit feedback to regulate the output voltage, munaully starting it without attaching it to the motherboard could cause damage to the power supply.



Last edited by zonko at Today at 12:18 pm

thanks zonko, it works since i hooked it up to the mobo, luckily i didn't burn it up before since i just plugged it in.

Nowadays new powersupplys like the ATX need to be connected to the MB to have power...