Service and troubleshooting
8.8 EST3 Installation and Service Manual
interaction between the supplies. Under most conditions, a
defective power supply will be identified by the system, and
annunciated as a trouble. The system may continue to operate
nearly normally, as the battery connected to the faulty supply
will automatically be switched into the circuit, as the load
demands.
Table 8-1: Nominal primary and booster power supply
voltages
Test Point Voltage
Rail Power 25 - 26.4 Vdc w/AC power on
Auxiliary Power 25 - 26.4 Vdc w/AC power on
Battery 27.3 V (battery under charge @ 25 °C)
Table 8-2: Primary Power Supply module troubleshooting
Problem Possible cause
Supply will not operate from
AC line
1. AC line fuse F2 (3.15A slow blow) open
2. Rectified DC fuse F3 (3.15A slow blow) open
RX or TX LED OFF
No communication between
3-PSMON and CPU
1. Defective or poor connection on ribbon cable between
3-PSMON and 3-PPS
2. 3-PSMON Defective
3. 3-PPS Defective
Auxiliary and Rail voltage low 1. Excessive load causing supply to fold back
2. Power Cable between 3-PSMON and 3-PPS loose or
defective
3. Booster Supply failure causing primary supply to fold back
Batteries will not charge 1. System in alarm mode
2. Fuse F1 (8A) on 3-PPS open
3. 30 to 60 Ah battery installed, 10 to 29 Ah battery specified in
SDU
4. Battery shorted
5. Battery not wired to power supplies correctly (only wired to
BPS/M)
System will not operate on
batteries
1. Battery voltage below 18 Vdc. (system automatically turns off
when batteries too low to properly operate system)
2. Fuse F1 (8A) on 3-PPS open
3. Batteries connected before AC power energized
4. Battery temperature too high
5. Defective batteries
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