How to switch on an ATX power supply without a motherboard?

This is a much needed answer for the people who are dealing with computer hardware. It is always good to know how to turn on a power supply unit (PSU) without the help of a motherboard when it comes to troubleshooting.
It’s pretty simple. The following picture shows a 20pin ATX connector.



What you have to do is short circuit the 14th (Green) and 15th (Black) pins using a wire as follows.





In 24 pin connector you can short circuit the 16th (Green) and 17th (Black) pins to turn on.