Alpha Technologies VMX Series - Manual (Page 52)

52 017-940-B0-001, Rev. A
6.0 VMX Power Supply Maintenance, continued
6.8 Replacing the Metal Oxide Varistors
The Power Distribution Board (PDB) uses three Metal Oxide Varistors (MOVs) for lightning
suppresson. If the MOVs fail, Alpha offers a replacement board option to bring the unit back
into service.
Tools Required: #2 Phillips screwdriver
Wire cutters
Fig. 6-1, MOV Removal
Before proceeding, verify all power has been removed from the power supply by
unplugging the power supply from the AC power source and disconnecting the battery
connector. Failure to do so could expose the technician to potentially lethal voltages.
WARNING!
Fig. 6-2, MOV Replacement
P3
P9
P8 (not shown)
Procedure:
1. Remove all power to unit. Turn off battery breaker and unplug battery connector. Unplug
line cord and remove all front panel connectors.
2. Remove the screws securing the power supply front panel. Set the screws aside in a safe
location.
3. Tip the front panel forward to gain access to the Power Distribution Board.
4. Remove the damaged MOVs using your wire cutters. See Fig. 6-1.
5. Replace with the MOV replacement card option (Alpha P/N 704-804-20). Position the
card over P3, P9, and P8 and seat fi rmly as shown in Fig. 6.2.
6. Replace the front cover.
Use a backup power source at this time as the VMX will not provide any power during this peocedure.
NOTE: