Making a AT Test PSU
 

Modders are always looking for a way to test lights, parts, or LEDs for lighting effects. No one uses the AT standard anymore but those Power Supplies are still available, either from old machines or real cheap. For $12 USD or less you can build one with new parts or if you already have the PSU it is only the cost of the switch.

Don't these PSU's need a load on the different voltage lines like ATX PSU's need?

There are much ATX supply's who have a resistor allready inside the supply, so it's not like all ATX supply's need a power resistor in order to make them boot or work proper.