ternal power connected to the aircraft and
using Test Set, Transponder AN/APM-
The RT859/APX-72 requires a pressuriza-
123A(V). For external power, refer to the ap-
tion of 5 psig when aircraft is operating at alti-
plicable manual covering the aircraft. Perform
tudes in excess of 30,000 feet. Apply a pressure
the following procedures and checks in the
gage to valve on front of RT859/APX72 (fig.
order given. If the correct response is not ob-
22) and read value of pressure. If value of
tained in any of the checks, refer to the trouble-
pressure exceeds 5 psig, bleed pressure until
shooting chart (para 318) for corrective
proper value is reached. If value of pressure is
less than 5 psig, apply air pressure until proper
(1) Preliminary procedures (para 3-10).
value is obtained. Ensure that air is free of
(2) Starting procedure (para 311).
moisture and contaminants.
(3) Receiver-Transmitter, Radio RT
859/APX72 tests (para 312).
Inspect the exterior of the RT859/APX-72
(4) Stopping procedure (para 313).
and MT3809/APX72 or MT3849/APX72.
b. Alternate Performance Check. If the test
The exterior surfaces should be free from
equipment called for in the performance checks
moisture, dirt, grease, and fungus.
above is not available, an alternate perform-
ance check, using the local transponder inter-
a. Remove dust and loose dirt with a clean,
rogation equiprnent, can be made. To carry out
this alternate performance check, follow the
Warning: Cleaning compound is flammable
procedures given in paragraph 314. If the cor-
and its fumes are toxic. Provide adequate ven-
rect responses are not obtained, refer to the
tilation; do not use near a flame.
troubleshooting chart (para 318) for correc-
b. Remove dirt from the connectors with a
soft bristled brush.
3-10. Preliminary Procedures
c. Remove grease, fungus, and ground-in
The AN/APM-123A(V) can be operated to
dirt from cases; use a cloth dampened (not
perform either radiation or nonradiation tests.
wet) with cleaning compound.
Refer to instruction manual with the AN/
APM123A(V) (appx A). The difference be-
3-8. Touchup Painting Instructions
tween the operations for the radiation and non-
Note: Refer to the cleaning and refinishiux practices
radiation test is the means of coupling RF
specified in applicable manual (appx A).
energy between the AN/APM123A(V) and
Antenna AT-884A/APX (or equivalent). °Free-
a. Remove rust and corrosion from metal
space coupling for radiation tests are per-
surfaces by lightly sanding them with No. 000
formed using an adjustable antenna mounted
on ths front panel of the AN/APM123A(V).
b. Brush two thin coats of paint (enamel,
Nonradiation tests are performed either by di-
lusterless gray, Federal Standard 595, color
rect cable-attenuator coupling to the RT859/
36231) on the bare metal to protect it from fur-
APX72 ANT. J5 connector or by an antenna
test hood provided for the AT884/APX44
(or equivalent) type antennas.
3-9. Power-On Inspection
Note: All references to the AN/APM-123A(V)
apply to the AN/APM-l23A(V) 1, 2, or 3, as appli-
( 1 ) Unsrew the relief valve of the AN/
APM-123A(V) two turns to release
a. Performance Checks. The performance
any internal pressure.
checks listed below are performed with ex-