MKS 651C, Instruction Manual, Page: 123 / 172

Chapter Eight: Valve Failsafe Battery Back-up
Option Battery Replacement
109
Battery Replacement
Opening the Unit
Warning
The 651 unit has lethal voltages inside. Servicing of the unit
must be performed by qualified personnel only.
To avoid an electrical shock, disconnect the power line
before opening the unit.
1. Turn the power off.
2. Disconnect the AC power cord.
Caution
To avoid damage to sensitive internal components, personnel
should be grounded through a safety impedance while working
inside the 651 unit, and the unit itself must be static-free.
3. Remove the two Phillips screws located at the top of the rear panel.
4. Disengage the cover from the rear chassis by lifting it up from the clips.
5. Remove the top cover by firmly pulling it up and back to clear the top of the connector
plates.
6. Locate the area of the unit where the chassis splits (to the rear of the front panel) and
remove the two screws on both sides of the front panel as well as the two screws on both
sides of the battery backup housing.
7. Slide the front panel out far enough to enable the ribbon cable to lay flat.
8. Slide the battery backup housing out about an inch.
9. Disconnect the battery power bus interface from the battery backup circuit board.
10. Unsnap the ribbon cable connector.
11. Pull both the front panel module and the battery backup housing away from the card
cage/power assembly.
12. Remove the screw located on the left side of the housing.
13. Orient the housing on its side, and remove the two visible screws.