d. Quadrant, M17, (fig. 3-39).
While purging the quadrant, ensure the pressure
relief valve is working by checking for nitrogen
gas escaping from the valve.
Figure 3-39 M17 and M18 Quadrants
(1) Perform purging and charging procedure para
(2) Purge instrument at 7 psig for 5 minutes.
(3) Turn pressure regulator off (CCW) and note when
relief valve closes.
(4) If relief valve closes before reaching 1 psig, re-
move hose assembly and depress valve core until all pres-
sure has escaped.
(5) Charge instrument at 1 psig for 60 seconds.
(6) Leak test for a minimum of 5 minutes.
e. Quadrant, M18 (fig. 3-39). Refer to para
3-11. d. for procedures.
(1) Optical Cavity (fig. 3-40).
See appendix C for Service Kit containing re-
placement parts for M1 and M1A1 Tanks.
Figure 3-40 Laser Rangefinder Optical Cavity
(a) Remove cover and check lens for cracks and
breaks. If damage is evident, do not attempt purging and
Perform purging procedure para 2-5.c.
Remove inlet plug and preformed packing.
Install valve extension on inlet port.
Attach hose assembly to valve extension.
Loosen, but do not remove sealing screw.
Purge instrument at 5 psig for 5 minutes.
While purging, leak test lens area.
Remove hose assembly and valve extension from
(j) Reassemble by tightening sealing screw and in-
(k) Install inlet port cap. Install inlet plug with pre-
formed packing attached and outlet screw with preformed