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.

Front Off

Front and left side with vents

Back with ATX input and right side with fan

Inside from the bottom