Bad Power Supply? 2

[TriRyche]

First time builder. Excuse my thickness!
I have an ATX case with a 420W power supply.
If I plug it in, should the fan on the power supply come on and should the extra power cables have power to them? Or does the mobo have to be all set first?
Thanks for your help,
Rich

 

[rclarke250]

The power supply will not come on or have any voltage except the stby 5 volt line to the system board,until the system board is connected and the power button pressed. It has a "soft power switch". the switch on the back of the power supply is for removing the AC power to the power supply circuitry,so you wouldn't have to unplug the power cord if you wanted to add memory,or an adapter card. since there is power to the system board at all times unless you remove the AC source,and you will damage the system.

 

[paparazi]

The power supply has to be "switched" through the motherboard and front panel switch to activate the PSU although there is a trick whereby you bridge the single green and a black with something like a paperclip in the main plug (that connects to the motherboard) this should bring the PSU to life.
Note* most but not all PSU's have this single green wire.
Martin

Replying helps further our knowledge, without comment leaves us wondering.

 

[TriRyche]

Thanks a bunch!!

 

[PeteWeedon]

TriRyche:

Are you trying to test the power supply on its own, i.e. with nothing connected to any of the power connectors?

The power supply must have some load on it or else it will not stay switched on. Some PSUs need to be delivering a minimum load current on the main 5V line before they will regulate properly, some need a bit of load on the 12V line as well.

Some PSUs even tell you their load current minima on the rating label!


Best regards,

Pete W.

If you can keep your head when all about you are losing theirs - you haven't seen the latest Change Note!