PSU Testing

Written by:  Gary Britton

Warning: Before attempting the following PSU test, power the system off and pull the power plug or flip the PSU switch off, whichever applies.

I have been struggling with a new build and got to PSU testing.

Here’s how to test yours if suspect. The PSU won’t power on unless it is under load or you jumper the main connector as shown below. The common thing to use is a paper clip bent in a “U” shape and can be inserted in either side of the plastic connector.


There will be one green wire, jumper it to any black one. This will allow the PSU to power up and its fan will run. If it has an on/off switch, confirm if it is ON. If the EPS 12V 4/8 pin is connected to the motherboard your CPU fan may run.

It is a better test if you use a digital multi meter after you have the PSU running to check actual volts output at the pins. Touch the “-” lead to any black wire pin then the “+” to each of the other colored pins and take a reading. They should be ±5% of listed voltages.

The diagrams below show the current ATX configurations in use.



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s