TM 11-840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective action
c. Defective Remote Switching
c.
Replace Remote Switching
Control C-6989/TPN-18.
Control C-6989/TPN-18.
10 a.
a. Ferrite control R123 in Radar
a.
Weak radar returns on either
Check ferrite control voltage at
azimuth or elevation, or both
TP103 and TP104 as described
azimuth and elevation with
818/TPN-18 misadjusted.
normal receiver sensitivity,
control voltage is not correct,
normal magnetron current
refer to TM 11-5840-281-12 for
indicated, and equipment
alignment instructions.
tuned up. Azimuth-elevation
normal.
b.
b.
b.
Voltage indication at (+) test-
Defective Remote Switching
On master Control-Indicator C-
point TP103 and (-) testpoint
Control C-6989/TPN-18.
6988/TPN-18, place SCAN
TP104 may or may not be
MODE switch to NORM and
abnormal.
SCAN switch to OFF Manually
position azimuth Antenna AS-
1292/TPN-18 fully. Place
FUNCTION selector on
20000Ω/VDC position and insert
probe to 250VDC connector.
terminal 1 (negative) and
terminal 3 (positive) of ferrite
switch S102.Multimeter TS-
52B/U should indicate
approximately 95 vdc with correct
polarity. If voltage is excessively
high or low, or polarity is
incorrect ,replace Remote
Switching Control C-6989/TPN-
18 and realign equipment.
a.
Measure voltage at SUM GAIN
a.
Defective gain control circuit i n
testpoint TP-3902 in sensitivity
11 Weak radar returns on azimuth,
master Control-Indicator C-
time control circuit card in Radar
radar returns normal on elevation
6988/TPN-18.
on both Control-Indicators C-
TPN-18 (reference to chassis
6988/TPN-18.
ground) with IF GAIN-AZ control
on master Control-Indicator C-
6988/TPN-18 rotated fully ew,
SCAN MODE switch placed to
NORM, STC to OFF, and
18stopped in midscan. Negative
voltage at SUM GAIN testpoint
should be near zero volt, and
should increase as IF GAIN-AZ
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-Indicactor C-7012/TPX to
position (1 of 2) which selects
other Control-Indicator C-
6988/TPN-18 as master. If
condition is corrected, trouble is
in IF GAIN-AZ control circuit of
control Indicator C-6988/TPN-
18.If trouble still exists, perform
step b below.
b.
Replace sensitivity time control
b.
Defective sensitivity time control
circuit card or RemoteSwitching
circuit card or Remote Switching
Control-Indicator C-989/TPN-18.
Control-IndicatorC-6989/TPN-18
3-4