TM 11-5840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective actio n
MASTER IND selector switch on
Indicator Control C-7012/TPX to
alternate position (1 or 2, as
applicable). If condition still exists,
perform b below.
b. Defective ftc relay K10402 in video
b. Replace video amplifier circuit card
amplifier circuit card.
in Radar Receiver-Transmitter RT-
818/ TPN-18.
a. Ftc adjustments in video amplifier
a. Perform video amplifier alignment
19 Ineffective or poor ftc response in
wide-pulse operation, narrow-pulse
circuit card misaligned.
(para 8-43). If condition still exists
operation, or both.
or alignment is not possible,
replace video amplifier circuit card.
b. Defective narrow-pulse relay K1401
b. Replace video amplifier circuit card.
in video amplifier circuit card.
Observe signal at DET VIDEO test-
Low sum receiver channel
20 Low video amplitude (less than
point TP1402 on video amplifier
performance
1.5v peak) or low receiver noises
circuit card with IF GAIN-AZ and IF
level (less than 0.5v peak) at FTC
GAIN-EL controls fully cw. If
VIDEO testpoint TP1408.
receiver noise level is 0.2v peak
nominal or greater, replace video
amplifier circuit card. If receiver
noise level is less than 0.2v peak
nominal, refer to item No. 17.
a. Defective EL TARGET control
a. If
two
Control-Indicators
C-
21 EL TARGET control on master
circuit in master Control-Indicator
6988/TPN-18 are installed in
Control-Indicator C-6988/TPN-18
C-6988/ TPN-18.
Landing Control Central AN/ TSQ-
has no effect on elevation display
71A, select other Control-Indicator
video when rotated from WIDE to
C-6988/TPN-18 as master by
NARROW.
placing MASTER IND selector
switch on Indicator Control C-
7012/TPX to alternate position (1 or
2, as applicable). If condition is
corrected, trouble is in EL TARGET
control circuit of Control Indicator
C-6988/TPN-18.
b. Defective difference receiver
b. Replace
difference
receiver
channel mixer crystals CR123 and
channel mixer crystals CR123 and
CR124.
CR124.
c. Difference receiver channel
c. Perform difference receiver channel
misaligned.
alignment (para 3-34).
d. Defective Intermediate Frequency
d. Replace
defective
unit
as
Amplifier AM-3338/TPN-8,
applicable.
Intermediate Frequency Amplifier
AM-3837/TPN-8 (difference
channel), or sensitivity time control
circuit card.
e. Defective elevation Antenna AS-
e. Refer
to
higher
category
1291/ TPN-18.
maintenance.
a. Defective IF GAIN-AZ or IF GAIN-
a. If
two
Control-Indicators
C-
22 IF GAIN-AZ control or IF GAIN- EL
EL control circuit in master Control-
6988/TPN-18 are installed in
control or both IF GAIN-AZ and IF
Indicator C-6988/TPN-18.
Landing Control Central AN, TSQ-
GAIN-EL controls have no effect on
71A, select other Control-Indicator
display video.
C-6988/'TPN-18 as master by
placing MASTER IND selector
switch on Indicator-Control C-
7012/TPX to alternate position (1 or
2, as applicable). If condition is
corrected, trouble is in IF GAIN-AZ
or IF GAIN-EL control circuit of
Control-Indicator C-6988,TPN-18.
3-7
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