TM 11-5840-281-35/1
(20) On electronic control amplifier, adjust
3-27. Precision Scan Mode Alignment
BIAS control R8802 for indication of 15 vac on vtvm.
(21) Adjust BAL control R8803 for null
a. Test Equipment Required. Oscilloscope AN/
indication on vtvm (null is approximately 4 to 5 turns on
USM-140B (oscilloscope).
BAL control). If multimeter indication drops to 0 vac
b. Equipment Conditions and Connections.
before sharp null is observed (scr firing point), rotate
(1) Radar Set AN/TPN-18 turned on. Re-
BIAS control R8802 small amount in cw direction and
move front and rear covers on Receiver-Transmitter RT-
readjust BAL control R8803 for null indication.
818/TPN-18.
(22) On vtvm, place RANGE switch to 10V.
(2) On Radar Receiver-Transmitter RT-
Readjust BIAS control R8802 for an approximate
818/TPN-18, control panel, place SCAN switch to OFF.
indication of 3 vac on vtvm.
Place AZ DRIVE POWER circuit breaker (on drive motor
(23) Repeat (21) and (22) above until null
amplifier) to OFF.
indication is approached while observing decreasing
(3) On master Control-Indicator C-6988/
voltage on vtvm between approximately 2 and 3 volts ac.
TPN-18 Pulse Generator 0-1333/TPN-18, SCAN MODE
(24) Disconnect vtvm.
switch placed to 60 AZ and SCAN switch placed to
(25) On Radar Receiver-Transmitter RT-
OFF.
818/TPN-18 control panel, place SCAN switch to OFF
(4) On azimuth Antenna Drive TG-113/
and place MAIN POWER circuit breaker to OFF.
TPN-8, data cover removed for access to azimuth
(26) Install electronic control preamplifier
synchro B1001.
(previously removed in step (14) above) in Radar
(5) On elevation Antenna Drive TG-114/
Receiver-Transmitter RT-818/TPN-18.
TPN-8, synchro cover removed for access to 10-degree
(27) On Radar Receiver-Transmitter RT-
synchro B502 and 35-degree synchro B503.
818/TPN-1S control panel, place MAIN POWER circuit
(6) Oscilloscope connected as shown in
breaker and SCAN switch to ON.
(28) Observe that azimuth Antenna AS-
c. Procedure.
1292/TPN-8 remains completely stopped.
(29) On Radar Receiver-Transmitter RT-
NOTE
818/TPN-18 control panel, place SCAN switch to OFF.
(30) On electronic control preamplifier,
When in precision scan (SCAN MODE switch
rotate FINE BAL control R7558 to midposition.
placed to NORM, 35 EL, or 60 AZ), elevation
(31) Adjust COARSE BAL control R7546 to
Antenna AS-1291/ TPN-8 and azimuth Antenna
AS-1292/ TPN-8 may be positioned by hand by
(32) On Radar Receiver-Transmitter RT-
rotating knurled end of elevation Antenna Drive
818/TPN-18 control panel, place SCAN switch to ON.
TG-114/TPN-8 drive motor shaft (located under
(33) On Remote Switching Control C-6989/
cover on right side of elevation Antenna Drive
TPN-18, rotate SEARCH RPM control R4059 in cw
TG-114/ TPN-8, as viewed from front of Radar
direction until azimuth Antenna AS-1292/ TPN-8 rotates
Receiver-Transmitter RT-818/TPN-18).
cw at approximately 16 rpm, as timed with stopwatch.
(1) On oscilloscope, place controls to
NOTE
positions indicated in (a) through (j) below:
(a) POWER: ON.
Do not replace covers on Radar Receiver-
(b) SWEEP MODE: PRESET.
Transmitter RT-818/TPN-18 until alignments and
(c) TRIGGER SOURCE: INT.
adjustments are completed.
(d) HORIZONTAL DISPLAY: X1.
(e) EXTERNAL VERNIER: CAL.
(I) SWEEP TIME MILLISECONDS/ CM: .2.
(g) SWEEP TIME VERNIER: CAL
3-34
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