This 11-155 Voltage Testing PDF shows the test points to measure the voltages in the 11-155 power supply which is used on the older PHI 595 and 600 scanning auger systems.

Procedure:

 Slide the 11-155 power supply  out so that the front of the unit is resting on the floor, and the back of the unit is still in the rack. Remove the top cover.

Turn on the RBD110 main power and measure the voltages as shown in the above drawing. The 5 volt supply usually is between 5 and 5.4 volts DC. The plus and minis 20 volts supplies are usually between 19.5 and 20.5 volts DC. All supplies should have less than 10 mV AC ripple.

If you have a bad 20V or 5V power supply, RBD Instruments has replacement units in stock.

Bonus – here are the 11-155 Scanning System Power Supply Schematics