To start the light, close the remote manual switch,
then turn the starter counterclockwise on the rear of
the starter unit. (See fig. 2-3.) Release the starter
switch as soon as the lamp arcs. Be sure the starter
switch returns to its previous position; otherwise, the
higher current required to start the lamp may damage
Initially, the lamp burns only at about 25 percent
of designed intensity. It takes 2 to 3 minutes to reach
The light should not be elevated or depressed more
than 10 degrees for extended periods of time because
the life of the lamp is reduced considerably at extreme
angles. Operate the shutters the same as you would the
incandescent lamp shutters. To turn off the lamp, open
the remote manual switch.
The 12-inch mercury-xenon arc searchlight
should be inspected and checked monthly. All screws,
especially those of the reflector clamps, focusing
mount, and lamp support, should be examined for
looseness. All screws and fastenings should be
checked after ship's guns have been fired.
Trunion and yoke bearings should be lubricated
with grease; see the MRC for the type of grease.
Replacement of the lamp must be performed as
explained in the applicable manufacturer's manual,
observing all precautions given.
When the return action becomes sluggish, the
shutter bearing and links should be lubricated. The
lubricant should be used sparingly and should not be
allowed to contact the envelope of the mercury-xenon
lamp. Should the shutters remain sluggish, replace the
The reflector and glass cover should be cleaned as
required by the MRC.
When considered necessary, the cover of the
ballast box should be removed and the five resistors
examined and tightened in their sockets. Wiring
should be checked and terminal screws tightened as
required. The packing glands at the cable entrances
should be kept secure and watertight.
Focusing is performed by means of a sliding
plunger at the rear of the focusing box on top of the
Maintenance is basically the same for the
manual-starting and automatic-starting, 12-inch,
mercury-xenon searchlights. For detailed differences
in the construction and operation of these two types,
see the applicable manufacturer's manual.
Electrical maintenance should be left to the
electricians unless a member of the signal gang is
qualified to do it by the engineer officer.
Figure 2-3.Starter unit for 12-inch mercury-xenon searchlight.