10055 - With the alarm/fault condition in question indicated on the SC-770 controller...

With the alarm/fault condition in question indicated on the SC-770 controller display, measure the voltages at the GPRB relay input connector J1.

• Gamma alarm (red strobe and speaker): Pin 1 (brown wire)
• Neutron alarm (blue strobe and speaker): Pin 2 (blue wire)
• Fault (amber LED): Pin 3 (white wire)

During a POST or alarm/fault condition, voltage should be ~3.5 VDC.
If no alarm or fault is indicated on the SC-770 controller display, voltage should be ~0.0 VDC.