TM 11-6625-2575-14
ORGANIZATIONAL MAINTENANCE
Section I. GENERAL REQUIREMENTS
b. Material. Trichloroethane.
Organizational maintenance is limited to proce-
WARNING
dures that can be accomplished without remov-
ing the instrument from its case. Operational
The fumes of trichloroethane are toxic.
checks are limited to those determinations which
Provide thorough ventilation whenever
can be made using the auxiliary equipment nor-
used. DO NOT use near open flame.
mally associated with the use of the AN/USM-
Trichloroethane is not flammable, but
203A.
exposure of the fumes to an open flame
5-2. Tools, Equipment, and Materials
converts the fumes to highly toxic, dan-
Required
gerous gases.
a. Tools Required. Allen wrenches: #6 (1/16
inch), #8 (5/64 inch).
Section Il.
EXTERNALLY SERVICEABLE DETAILS
5-4. Single Function Control Knobs
a. Single function control knobs are used on
a. The fuse which protects the instrument in
the following controls:
the event that excessive current is drawn from
the line is located on the rear panel.
(1) ATTENUATION control.
(2) BAND switch.
b. Remove the fuse by pressing down on the
cap and turning counterclockwise to the stop.
(3) EXTERNAL MARKER SIZE.
Withdrew the fuse and the cap, and then remove
b. All single function knobs are secured to
the fuse from its receptacle.
their shafts by means of recessed setscrews. Two
screws are used on the band switch and attenuator
c. The fuse is a type 3-AG, rated at 1 ampere.
controls, while only one is used on the external
(Littelfuse 312001)
marker size control. These screws require a #8
Allen wrench.
NOTE
See paragraph 1.11 for 230-volt opera-
c. The band switch and the attenuator con-
tion.
trols must be properly positioned on their shafts
before tightening the setscrews.
d. Insert the fuse in the receptacle of the cap.
(1) The band switch has only two posi-
e. Insert the fuse and cap assembly into the
tions, LOW and HIGH. The actual position of
receptacle at the rear of the instrument.
the shaft may be determined by temporarily
tightening one setscrew and establishing that the
f. Turn the cap until the two metal protru-
switch is in the counterclockwise position. The
sions mate with the notches in the receptacle.
setscrew is then loosened, the knob index lo-
Press down and turn clockwise to the stop.
cated to indicate the low position, and the knob
secured in this position.
g. If the fuse fails again when the instrument
is turned on, report the condition to higher cate-
(2) The attenuator controls are capable of
gory maintenance.
360 of rotation, and the 0-dB position must be
