TM 11-5840-281-35/1
Item No.
Trouble symptom
Probable trouble
Checks and corrective action
Defective rotating coil amplifier or
a. Check tubes V1604 through V1607
defective sweep generator circuit
in rotating coil amplifier.
10 40-mi range mark will not adjust to
card.
b. Replace sweep generator circuit
within 3/16 in. from edge of crt
card.
when ppi sweep is centered,
c. Repair or replace rotating coil
SCAN MODE switch placed to
amplifier.
SEARCH, and RANGE MILES
switch placed to 40.
a. Low output voltages from 18v
a. Check 18v voltage regulator
11 Sweep origin cannot be positioned
voltage regulator.
outputs.
off of rt by adjusting PPI
b. Misadjusted fixed coil
b. Perform fixed coil amplifier
CENTERING controls on Control-
amplifier............
alignment (pars 3-38).
Indicator C4988/ TPN-18.
c. Defective amplifiers Q1904 thru
c. Replace defective amplifier
Q1907 in Power Supply PP-
transistor.
3383/TPN-8.
12 Outer range marks on all range of
Defective rc networks in sweep
Replace sweep generator circuit card
ppi weeps do not fall within 1/4 in.
generator circuit card.
in applicable Pulse Generator O-
of each other.
1333/TPN-18.
13 Abnormal AZ TILT meter indication
Defective tilt data potentiometer R9101
Refer to paragraph 3-10, item No. 29.
on both Control-Indicaton C-
in antenna actuator on azimuth
6988/TPN-18.
Antenna AS-1292/TPN-8 or
defective slip-ring E1001 in
azimuth Antenna Drive TG-
113/TPN-8.
14 Abnormal AZ TILT meter indication
AZ TILT meter circuit in azimuth-
a. Perform azimuth tilt meter
on one Control-Indicator C-
elevation blanking pulse
alignment. Refer to TM 11-5840-
6988/TPN-18.
generator circuit card misaligned
281-12 for alignment instructions.
or defective.
b. Replace azimuth-elevation blanking
pulse generator circuit card in
applicable Pulse Generator 0-
1888/TPN-18.
15 LO TUNE control on matter
a. LO TUNE control on Radar
a. On Radar Receiver-Transmitter RT-
Control- Indicator C-988/TPN-18
Receiver-Transmitter RT-
818/TPN-18 control panel, place
does not have adequate tuning
818/TPN-18 control panel
LOCALREMOTE switch to
range.
misadjusted or defective.
LOCAL and hold in LOCAL while
adjusting LO TUNE control for
maximum crystal current
indications on XTAL CUR meter.
b. Abnormal -200v supply voltage
b. Check -200v supply voltage at -
200v testpoint TP4303 on Power
Supply PP-3382/TPN-8.
c. Defective local oscillator tube V103
c. Refer to higher category
in Radar Receiver-Transmitter
maintenance.
RT-818/TPN-18.
16 Low or no receiver noise on both
Low sum channel performance
Refer to paragraph 3-10, item No. 17.
Control-Indicators C-988/TPN-18.
17 Low or no receiver noise on one
Control-Indicator C-6988/TPN-18.
a. Mixer amplifier circuit card
a. Perform mixer amplifier alignment
misaligned or defective.
corrected, replace and align
mixer amplifier circuit card.
b. Low +300v supply from rotating coil
b. Check 300v testpoint TP1601 on
amplifier to crt.
rotating coil amplifier.
c. Defective VIDEO GAIN control
c. Replace VIDEO GAIN control R603.
18 Abnormal indication on HV ON
R603.
indicator.
Defective radar transmitter
Refer to paragraph 3-10, item No. 25.
19 Apparent width of radar target do
not decrease when FTC switch
on master Control-Indicator C-
Misaligned or defective ftc circuit
Refer to paragraph 3-10, items No. 18
6988/TPN-18 is placed to ON.
and 19.
3-12
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