This is an adapter that I use to breakout +3v, +5v, and +12v from a pc power supply as well as monitor voltage and amperage. Basically a cheap lab bench power supply.

The ground for each voltage goes through a shunt which is connected to the dial. The commons for the dial are connected to the amperage and voltage leads on the display. The standby light is connected to the +5vsb(pin 9), the status to pwr_ok(pin 8) and the switch shorts ground and pwr_on(pin 14).  There is also a 10w ceramic resistor between +5v and ground to stabilize the power suppy when there is a low load. This is also why there is a fan in the case as the resistor gets very hot.

 

atx_adapter_front_off
Front when off
atx_adapter_left
Front and left side with vents
atx_adapter_back
Back with ATX input and right side with fan
atx_adapter_inside
Inside from the bottom