TM 1-1520-238-10
4-74
FILTER
FILTER
CONTROL
M01-187
Figure 4-22.
Radar Warning Discriminator On
Mode Display
4.37.4 AN/APR-39(V)1 Self-Test Operation.
The self-
test checks all RW set circuits except antennas, high-pass
filters and detectors in the high band receiver, bandpass
filter and detector in the low-band receiver, analysis signal
commutator, and high and low-band blanking circuits. The
self-test procedure is done before operation and when
any malfunction is detected. A self-test display is shown in
figure 4-23.
a. Self-test procedures are as follows:
1. PWR switch – ON. Panel lights illuminate.
2. DSCRM switch – OFF. Wait 1-minute for war-
mup. Monitor display CRT and audio.
3. SELF-TEST button – Press and hold.
a. FWD and AFT strobes appear, extending to
about the third circle on the display grati-
cule, and a 2.5 kHz (approximately) PRF
audio is present immediately.
b. Within about 6 seconds, alarm audio is
present and the MA light starts flashing.
c. Display BRIL control – Turn cw and ccw.
Strobes brighten (cw) and dim (ccw) as con-
trol is turned. Set BRIL control for desired
brightness level.
FILTER
FILTER
CONTROL
M01-188
Figure 4-23.
Radar Warning Self-Test Mode Display
d. AUDIO control – Turn between max ccw
and max cw. Audio will not be audible at
max ccw and clearly audible at max cw.
e. SELF-TEST pushbutton – Release. All indi-
cations cease.
4. DSCRM switch – ON.
5. SELF-TEST button – Press and hold.
a. Within about 4 seconds a FWD or AFT
strobe (either may appear first) and a 1.2
kHz (approximately) PRF audio will be pres-
ent.
NOTE
Occasionally, during the period between
pressing SELF-TEST and appearance of
the first strobe, a distorted dot on the display
and intermittent audio will be present. This
is not a fault isolation.
b. Within about 6 seconds, the other strobe will
appear and the PRF audio frequency will
double.
c. Several seconds later alarm audio will be
present and the MA light starts flashing.
d. SELF-TEST button – Release. All indica-
tions cease.
6. PWR switch – As desired.
