1-8. DIFFERENCES BETWEEN MODELS
M145/M145A1 Telescope Mount. The M145A1 has a modified quadrant support assembly that is stabilized through use
of a V-bearing, spring retainer, and new gearshaft assemblies.
M118A2/M118A3 Elbow Telescope. The M118A2 uses incandescent lamps and light conductors for illuminating of
reticle and level assembly. The M118A3 uses light emitting diodes mounted on circuit board assemblies that are not
replaceable without opening the telescope assembly.
M117/M117A2 Panoramic Telescope. The major differences between the M117 and M117A2 panoramic telescopes are
external. The upper housing and electrical assemblies vary in configuration. When repairs are made on early production
models, update in accordance with most recent procedures, MWOs and ECOs.
M15 Fire Control Quadrant. M15 quadrants within the categories listed below have design differences as stated. As a
minimum, all instruments must be provided with a means for removing moisture and condensation at time of repair.
(1) Early Configurations.
These M15 quadrants were altered to provide removal of moisture and condensation utilizing one of the following
(a) Utilizing a valve assembly in the cover assembly and utilizing one of two identification plate screw holes as the
(b) Utilizing latest configuration of shafts, part numbers 10553923 and 10553932.
(c) M15 quadrants received with purging facilities utilizing shafts, part numbers 10553923 and 10553932, or with
serial numbers above 5500, will not be altered to use purging valve in cover assembly. M15 quadrants not having purging
facilities will be altered using either of the above methods.
Configurations Without Purging Ports.
These M15 quadrants do not provide a means to purge and must be altered to provide purging capabilities by installing
latest configurations of shafts, part numbers 10553923 and 10553932.
(3) Latest Configuration.
These M15 quadrants incorporate the latest design improvements which provide the means to purge and charge. They
are in accordance with repair instructions and illustrations contained in this TM. The design change incorporates preformed
packings and gaskets to hermetically seal the instrument and locate the valve assembly and exhaust port on pivot shafts of the
mounting bracket. This configuration also incorporates an overlay and change of lamps from incandescent to LEDs.
e. M42 periscope. The difference between early production models and later models is location of the purging valve. The
early model requires use of an adapter to attach the purging hose; the later model does not require an adapter.