TM 11-5840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective action
a.
12 Weak radar video on elevation, radar
Defective gain control circuit in
a.
Measure voltage at SUM GAIN
video normal on azimuth on both
master Control-Indicator C-
testpoint TP3902 on sensitivity time
Control-Indicators C-6988/TPN-18.
6988/TPN-18.
control circuit card (reference to
chassis ground) in Radar Receiver-
Transmitter RT-818/TPN-18 with IF
GAIN-EL control on master Control-
Indicator C-6988/TPN-18 rotated fully
cw, SCAN mode switch to NORM, STC
to OFF, and elevation Antenna AS-
1291/TPN-8 stopped at midscan.
Negative voltage at SUM GAIN
testpoint TP3902 should be near 0 volt,
and should increase as IF GAIN-EL
control is rotated ccw. If voltage at
SUM GAIN testpoint TP3902 is
abnormal and Control-Indicators C-
6988/TPN-18 are installed in Landing
Control Central AN/TSQ-71A, place
MASTER IND select switch on Control-
Indicator C-7012/TPX-44 to position (1
or 2) which selects other Control-
IndicatorC-6988/TPN-18as master. If
condition is corrected, trouble is in IF
GAIN-EL control circuit of Control-
Indicator C-6988/TPN-18. If trouble still
exists, perform step b below.
b.
Defective sensitivity time control
b.
Replace sensitivity time control
circuit card or Remote Switching
circuit card or Remote Switching
Control-Indicator C-6989/TPN-18.
Control-Indicator C-6989/TPN-18.
13 Azimuth and elevation sweeps switch
Defective angle volts circuit in Pulse
a.
Check for presence of angle voltsat
Generator O-1333/TPN-18 in
between azimuth and elevation but
AZ-EL ANGLE VOLTS test--point
malfunctioning Control-Indicator C-
do not scan on one Control-
TP1102 on top deck of Pulse
6988/TPN-18.
Indicator C-988/TPN-18 in precision
Generator in applicable Control-
scan modes (SCAN MODE switch
Indicator C-6988/TPN-18.
on master Control-Indicator C-
b.
If angle volts are present at AZ-EL
6988/TPN-18 placed to NORM, 35
ANGLE VOLTS testpoint
EL, or 60 AZ). Scan on other
TP1102,replace fixed coil amplifier.
Control-Indicator C-6988/TPN-18 is
If trouble is not corrected, refer to
normal.
higher category maintenance.
c.
If angle volts are not present at AZ-
EL ANGLE VOLTS testpoint
TP1102, replace search-precision
relay K1102 in application Pulse
Generator O-1333/TPN-18. If
trouble is not corrected, refer to
higher category maintenance.
Defective azimuth-elevation switching
14 Azimuth and elevation sweeps switch
a.
Check for presence of angle volts at
relay K4015 in Remote Switching
between azimuth and elevation but
ANGLE VOLTS the testpoint TP703
Control C-6989/TPN-18.
do not scan in precision scan
on azimuth and elevation electronic
modes (SCAN MODE switch on
filters.
master Control-Indicator C-
b.
If angle volts are present at ANGLE
6988/TPN-18 placed to NORM,35
VOLTS testpoint TP703, replace
EL, or 60 AZ) on both Control-
Remote Switching Control-Indicator
Indicators C-6988/TPN-18.
C-6988/TPN-18.
-35v supply to azimuth angle data
15 Abnormal vertical deflection of
a.
Check angle data voltage at ANGLE
potentiometer R1001 and elevation
azimuth and elevation sweeps in
DATA testpoint TP702 on azimuth
angle data potentiometer R501 is
precision scan modes on both
electronic filter with azimuth
defective.
Control-Indicators C-6988/TPN-18
Antenna AS-1292/TPN-8
3-5
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