TM 10-6640-239-13 4-89 4-39.    GAS ALARM SYSTEM. This task consists of: a. Remove b. Install c. Test d. Calibrate INITIAL SET-UP Tools Required General Mechanics Tool Kit, (Appendix B, Section III, Item 1) Materials/Parts Required Lockwashers, (4) General Safety Instructions WARNING ELECTRICAL SHOCK Before  performing  any  maintenance  actions  on  electrical  equipment,  ensure  all electrical power has been turned off.  Failure to comply with this warning may result in serious injury or death. REMOVE 1. Remove Gas Alarm.  See Figure 4-30. a. Remove power from all equipment. b. Position all Main Power Panel circuit breakers to OFF. c. Shut down generator. d. Loosen latch (1) and swing open door (2) of gas alarm unit (3). e. Loosen captive release screw and swing panel out. f. Carefully remove circuit board. g. Tag and disconnect wires, by removing terminal screw, from the following terminals: Terminal board TB-1 A1, C1, R1, A2, C2, R2, and N Terminal Board TB-2 1, 5, 6, and 8 Disconnect shield wires from ground stud. Disconnect ground wires (green) at conduit retaining nut last. h. Loosen two conduit fittings and disconnect flexible conduit (4) and wiring to buzzer and power input. i. Reinstall circuit board, shut and latch alarm panel, and close door (2). j. Remove four screws (5), lockwashers (6), washers (7), and spacers (8) and carefully remove gas alarm (3).  Discard lockwashers. 2. Remove Gas Alarm Buzzer.  See Figure 4-31. a. Disconnect power input cable to laboratory. b. Remove four screws (9) and cover (10) from junction box (11). c. Remove mounting collar (12) and pull buzzer (13) from junction box (11) to gain access to wires. d. Tag and disconnect two wires from buzzer (13).