Service and troubleshooting 
EST3 Installation and Service Manual  8.9 
3-BPS/M Booster Power Supply module 
The transmit (TX) and receive (RX) LEDs on the Booster Power 
Supply Monitor Module should flicker, indicating normal two 
way communication activity with the CPU. 
[PSMONLED.CDR]
TX RX
TX RX
 
The booster power supply voltages are indicated in Table 8-1. 
Table 8-3 lists common problems with the booster power supply 
and booster monitor module. 
 
Table 8-3: Booster 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-BPSMON and CPU 
1.  Defective or poor connection on ribbon cable between 
3-BPSMON and 3-BPS 
2. 3-BPSMON defective 
3. 3-BPS defective 
Auxiliary and Rail voltage low  1.  Excessive load causing supply to fold back 
2. Power Cable between 3-BPSMON and 3-BPS loose or 
defective 
3.  Booster Supply failure causing primary supply to fold back 
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-BPS open 
3.  Batteries connected before AC power energized 
4.  Battery temperature too high 
5. Defective batteries 
 
CPU Central Processor module 
The CPU controls all the communication and processing of 
information for modules located in its cabinet. Token ring