TM 11-5840-360-14-1-1
a. LOCAL TEST: ON
6. Observe positive edges of squarewave signal
b. LOCAL PRF SELECTOR: MED
displayed on oscilloscope; adjust frequency control R9
c. MONITOR SELECT: MAG I
on Receiver Transmitter RT-1241 A6 Pulse Logic PCB
2. Connect multimeter, set to 50 Vdc scale,
to obtain the time noted in step 4 above between
between TP1 (+) on the Magnetron Heater Scheduling
positive edges of the squarewave signal.
PCB A5 and chassis.
NOTE
3. Verify test meter Ml reading is in the middle of
All test points and controls called
the green zone.
out in the remainder of this
4. Adjust output control A5R5 to obtain the
procedure are located at Receiver
following Vdc reading on multimeter:
Transmitter RT-1241.
+9.0 Vdc for EEV Magnetron
7. Set LOCAL TEST switch to OFF.
+12 Vdc for Ratheon Magnetron
8. Set LOCAL PRF SELECTOR switch to MED.
5.17.3.5 Local Oscillator Adjustment (V4). The following
9. Using a 10X probe, connect oscilloscope at test
steps align the local oscillator to the transmitter
point TP2 of Pulse Driver PCB A7; set oscilloscope for
operating frequency.
dc input coupling and 50V/division display.
NOTE
10. Set LOCAL TEST switch to ON; after 3.5minute
Observe settings of Switching Units
delay, adjust oscilloscope to display positive portion of
SA-2139 and refer to Table 3-3 to
modulator drive pulse.
determine which Indicator is serving
11. Adjust 550 ADJ control RI on Low Voltage
as master for Receiver Transmitter
Power Supply A3 to obtain pulse peak amplitude of
+150 volts.
RT 1241.
12. Adjust medium pulse adjust control R23 on
1. At master Indicator:
Pulse Logic PCB 13A6 to obtain a pulse width of 500
a. Set POWER switch to TX ON.
nsec from the peak of the leading edge to the base of
b. Set TUNE control to center of its range.
the trailing edge.
c. Set RANGE SELECT switch to 6 MILES.
13. Set LOCAL PRF SELECTOR switch to SHORT.
2. Connect multimeter, set to +10 Vdc scale,
Verify pulse peak amplitude is +150 + 5 volts on
between TP7 TUNE (+) and TP10 GND (-) test points at
oscilloscope.
Receiver Transmitter RT 1241.
14. Adjust short pulse adjust control R28 on Pulse
3. Disconnect output cable at J1 of A9 IF Amplifier
Logic PCB 13A6 to obtain a pulse width of 65 nsec from
Assembly; install BNC Tee connector on cable and
the peak of the leading edge to the base of the trailing
connect Tee at A9J 1.
edge.
4. Connect oscilloscope to Tee connector at A9J 1.
15. Set LOCAL PRF selector switch to LONG.
5. Turn local oscillator frequency adjustment (see
Verify pulse peak amplitude is +150 + 5 volts on
oscilloscope.
6. While observing multimeter, carefully turn local
16. Adjust long pulse, adjust control R25 on Pulse
oscillator frequency adjustment control counterclockwise
Logic PCB 13A6 to obtain a pulse width of 1000 nsec at
until multimeter deflection indicates presence of signal.
the peak of the leading edge to the base of the trailing
NOTE
edge.
A false signal node may be
17. Set MONITOR SELECT switch to MAG I.
encountered when adjusting the
18. Adjust high voltage OUTPUT V control A4R23
local oscillator cavity. This false
on High Voltage Power Supply A2 to obtain an M1 test
node will be indicated by presence of
meter reading in the middle of the green zone.
high level noise and no video targets
19. Set master Indicator POWER switch to OFF.
on the oscilloscope and CRT
Set LOCAL TEST switch to REMOTE ENABLE.
displays.
If this false node is
Disconnect oscilloscope. Set LOCAL PRF SELECTOR
encountered, continue turning the
switch to REMOTE.
frequency
adjustment
control
5.17.3.4 Magnetron Heater Scheduling PCB Adjustment
counterclockwise
until
the
(V4) - The radar duty cycle varies with the range scale
multimeter indicates signal presence
selected. The following steps align the Magnetron
at another control setting and video
Heater Scheduling PCB circuit to insure that the proper
targets are displayed on the
voltage level is applied to the magnetron filament for the
oscilloscope.
duty cycle in use. All test points and controls called out
7. Observe oscilloscope display and identify a non-
in the following steps are located at Receiver
saturating video target which is displayed during each
Transmitter RT-1241.
rotation of the antenna. If necessary, adjust receiver
1. Set switches as follows:
transmitter GAIN control to optimize target amplitude.
5-96
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