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TM 55-4920-400-13
Section V.
AVIATION UNIT MAINTENANCE (AVUM)
2-31. General. This section contains information
and procedures which must be followed to insure
that the test set remains in good operating condi-
tion. Maintenance consists of filling the oil reser-
voir when necessary, emptying the fuel filter
sumps, adjusting the safety relief system and peri-
odic calibration of gauges in accordance with appli-
cable military specifications. AVUM consists of
troubleshooting the test set, correcting detected
faults, and replacing parts and components when
necessary.
2-32. Filling Oil Reservoir. Whenever the oil
level of the reservoir falls below the minimum level
indicated on the reservoir, oil conforming to Specifi-
cation MIL-H-5606 must be added until the oil level
is again at proper level. To fill the reservoir, proceed
as follows:
a. Prepare test set for use in accordance with pro-
cedure given in paragraph 2-25.
b. Remove cover plate on right side panel of test
set to gain access to reservoir and filler port.
c. Unscrew cap nut from filler valve port and set
Fill and Run valve handle to Fill.
d. Attach filler hose to port from which cap nut
was removed, and tighten securely. Place filter end
of filler hose in container of oil conforming to Speci-
fication MIL-H-5606.
e. Set power switch (12, fig. 1-1) to ON. Observe
reservoir through window on right side panel; when
oil level is within points indicated, set ON-OFF
switch to OFF.
f. Disconnect filler hose from port, securely re-
place cap nut on filler valve port, and set Fill and
Run valve handle to Run.
g. Replace cover plate on right side of test set.
2-33. Emptying Sumps. The two test set filters
are equipped with sumps which permit only air to
enter the vacuum and pressure lines to the instru-
ments. If the oil occupies more than 50 percent of
the total glass area of the sumps, the sumps must be
emptied. To empty the sumps, proceed as follows:
a. Open test set panels to gain access to interior.
b. Loosen bottom screw of sump bracket, remove
sump, and empty oil from sump.
Dry Cleaning Solvent
Fed Spec P-D-P680
l Flammable - do not use near welding areas, near
open flames, or on very hot surfaces.
l Use only with adequate ventilation.
l Do not smoke when using it.
l Avoid prolonged or repeated breathing of vapors
l Use protective creams, wear aprons, and wear gog-
gles or face shield to protect the skin.
l Store in approved metal safety containers.
c. Clean bowl and filter with Varsol in accord-
ance with Federal Specification TT-T-291.
d. Replace sump and secure bottom screw
tightly to prevent leakage through sump gasket.
e. Operate test set for maximum vacuum using
altimeter and for maximum pressure using fuel
pressure gauge. Refer to paragraph 2-26 for oper-
ating procedures.
f. If maximum vacuum or pressure is not ob-
tained in paragraph d above, leakage probably ex-
ists at sump gasket. Tighten bottom screw of sump
to produce a complete seal.
g. Turn off test set. Replace panels which were
removed in paragraph a above.
Section VI.
RADIO INTERFERENCE SUPPRESSION
2-34. General. Radio interference suppression is
satisfactorily suppressed, there is no radiated or
the elimination, or reduction to a minimum, of elec-
trical disturbances produced by operation of the
equipment. These electrical disturbances are com-
posed partly of electrical waves in the radio fre-
quency range. They must be suppressed as they will
interfere with the proper operation of friendly radio
and radar equipment, and can be detected by an
enemy with electronic devices to give an accurate
location of the equipment. When the equipment is
conducted interference in the frequency range of
0.15 through 1000.0 megacycles at a distance of 5
feet from the tester.
2-35. Interference Suppression Com-
ponent. There is a filter mounted on the electric
motor and it provides a low resistance path to
ground stray currents created by the arc of the
motor brushes.
Change 1 2-7
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