TM 9-4940-568-20
2-44
Table 2-5. Generator Troubleshooting (CONT).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
3. OUTPUT VOLTAGE IS UNSTABLE.
1
The voltage adjusting rheostat (1) on the control panel is faulty.
Unlock the voltage adjusting screw on the front of the control panel and disconnect either
lead from the rheostat. Measure resistance between terminals 1 and 2 while turning the
adjusting screw fully one way and then the other. Replace the rheostat if it is open at any
point, or if resistance does not vary smoothly from zero to approximately 1,500 ohms for
sets with the SX460 voltage regulator (shunt excited) or 5,000 ohms for sets with the
MX321 voltage regulator (PMG–excited).
Voltage Regulator VR21 is faulty.
Replace voltage regulator. Notify Direct Support.
4. THE FIELD CIRCUIT BREAKER KEEPS TRIPPING.
Voltage Regulator VR21 is faulty.
Replace voltage regulator. Notify Direct Support.
5. THE PHASE CURRENTS ARE UNBALANCED.
The connected loads are distributed unevenly among the phases.
Shut down the set and redistribute the loads as evenly as possible.
Improper connections have been made at the generator output terminals.
Shut down the set and reconnect according to the reconnection diagram. See inside main
power switch panel.
A load has a ground fault or short circuit.
Service the faulty equipment as necessary.
