TM 11-840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective action
c.
Replace Remote Switching
Antenna Drive TG-113/TPN-18.
c. Defective Remote Switching
Control C-6989/TPN-18.
a.
Check ferrite control voltage at
Control C-6989/TPN-18.
10 a.
a. Ferrite control R123 in Radar
Weak radar returns on either
TP103 and TP104 as described
azimuth or elevation, or both
Receiver-Transmitter RT-
in para 4-6, step 6. If ferrite
azimuth and elevation with
818/TPN-18 misadjusted.
control voltage is not correct,
normal receiver sensitivity,
refer to TM 11-5840-281-12 for
normal magnetron current
alignment instructions.
indicated, and equipment
b.
On master Control-Indicator C-
tuned up. Azimuth-elevation
6988/TPN-18, place SCAN
relay gate operation is
MODE switch to NORM and
normal.
b.
b.
Voltage indication at (+) test-
Defective Remote Switching
SCAN switch to OFF Manually
point TP103 and (-) testpoint
Control C-6989/TPN-18.
position azimuth Antenna AS-
TP104 may or may not be
1292/TPN-18 fully. Place
abnormal.
FUNCTION selector on
Multimeter TS-352B/U to
20000Ω/VDC position and insert
probe to 250VDC connector.
Connect multimeter between
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
testpoint TP-3902 in sensitivity
time control circuit card in Radar
Receiver-Transmitter RT-818/
a.
Defective gain control circuit in
11 Weak radar returns on azimuth,
TPN-18 (reference to chassis
master Control-Indicator C-
radar returns normal on elevation
ground) with IF GAIN-AZ control
6988/TPN-18.
on both Control-Indicators C-
on master Control-Indicator C-
6988/TPN-18.
6988/TPN-18 rotated fully ew,
SCAN MODE switch placed to
NORM, STC to OFF, and
azimuth Antenna AS-1292/TPN-
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
b.
Defective sensitivity time control
MASTER IND select switch on
circuit card or Remote Switching
Control-Indicactor C-7012/TPX to
Control-IndicatorC-6989/TPN-18
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
circuit card or RemoteSwitching
Control-Indicator C-989/TPN-18.
3-4
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