TM 11-5840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective action
28 Antenna actuator on elevation
Perform Antenna AS-1291/TPN-
Antenna actuator limit switches
Antenna AS-1291/TPN-8 or
8antenna actuator alignment ( para
misaligned or defective.
azimuth Antenna AS-1292/TPN-8
continues to run beyond limits or
antenna actuator alignment ( para 8-
stops short of prescribed limits.
25) as applicable.
a. Observe voltage at AZ TILT DATA
29 AZ TILT meter indication on
Defective azimuth tilt data
testpoint TP2402 on az-el blanking
Control-Indicators C-6988/TPN-18
potentiometer in azimuth antenna
pulse generator in either Pulse
abnormally high or low.
actuator.
Generator O-1333/TPN-18. Voltage
should be approximately -1v
(reference to chassis ground) with
azimuth Antenna AS-1292/TPN-8
tilted all the way down (-1 deg).
b. If voltage in a above is abnormal,
perform Antenna AS-1292/TPN-8
antenna actuator alignment (par 3-
25).
c: If condition is not corrected by
alignment, replace and align
antenna actuator.
a. Observe voltage at EL
30 Blanked area in azimuth range
Defective elevation servo data
SERVODATA testpoint TP2401 on
marks miming or abnormal.
potentiometer in elevation antenna
az-el blanking pulse generator in
actuator.
either Pulse Generator O-
1333/TPN-18. Voltage should be
approximately -1v (reference to
chassis ground) with elevation
Antenna AS-1291/ TPN-8 servo to -
15 deg (indicated on elevation
protractor).
b. If voltage in a above is abnormal,
perform Antenna AS-1291/TPN-8
antenna actuator alignment ( para 3-
19).
c: If condition is not corrected by
alignment, replace and align
antenna actuator.
a. Misalignment of azimuth tilt
a. Perform azimuth tilt blanking and
31 Radar returns on azimuth display
blanking or elevation servo
elevation servo blanking
are not at maximum when elevation
blanking.
alignments. Refer to TM 11-5840-
servo position (blanked section of
281- 12 for alignment instructions.
elevation range marks) is
b. Defective elevation Antenna AS-
b. Refer to higher category
bracketing radar returns, or radar
1291/ TPN-8 or azimuth Antenna
maintenance.
returns on elevation display are not
AS-1292/TPN-8.
at maximum when azimuth servo
position (blanked section of
azimuth range marks) is bracketing
radar return.
Misalignment of azimuth protractor .............
Perform antenna system test ( para 4-
32 Incorrect bearing of radar return on
13). If elevation or azimuth
azimuth display in precision scan
protractor does not meet indicated
modes (NORM, 35 EL, and 60
performance standards, refer to
AZ) on both Control-Indication C-
higher category maintenance.
6988/TPN-18.
a. Adjustments on electronic control
a. Perform search scan mode
33 Azimuth Antenna AS-1292/TPN-8
preamplifier misaligned.
alignment (para 3-26).
rotates or creeps when SCAN
b. Defective electronic control
switch on Radar Receiver-
b. If trouble is not corrected by
preamplifier circuit card.
Transmitter RT-818/ TPN-18
alignment, replace electronic
control panel or master Control-
control preamplifier circuit card and
Indicator C-6988/TPN-18 is
perform search scan mode
placed to OFF.
alignment
3-9
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