TM 11-5840-281-35/1
(2) Loosen two knurled front panel screws
3-40. Mixer Amplifier Alignment
and pull Pulse Generator O-1333/TPN-18 as far out of
Control-Indicator C-6988/TPN-18 case as cabling will
allow.
a. Test Equipment Required. Oscilloscope AN/
(3) Loosen three of four linear locking
USM-140B (oscilloscope).
screws (socket-head screws) in cathode ray tube
b. Equipment Conditions and Connections.
mounting by reaching through access hole in top of
(1) Radar SET AN/TPN-18 turned on.
Control-Indicator C-6988/TPN-18 case. Bottom linear
(2) Rear cover of applicable Control-
locking screw must be reached through Pulse Generator
Indicator C-6988/TPN-18 removed for access to mixed
O-1333/TPN-18 compartment.
amplifier and controls.
(4) Gently push deflection yoke assembly
(3) At front of applicable Control-Indicator
for- ward until it touches bell of cathode ray tube, then
C-6988/TPN-18, Pulse Generator 0-1333/ TPN-18 pulled
pull deflection yoke back approximately /6 inch.
out for access to trigger delay generator.
(5) Tighten four linear locking screws.
(4) On master Control-Indicator C-6988/
(6) Push in Pulse Generator 0-1333/ TPN-
TPN-18 and Pulse Generator O-1333/TPN-18, place
18 and tighten two knurled front panel screws.
SCAN MODE switch to SEARCH, TRANS- MITTER
(7) On applicable Control-Indicator C-6988/
switch placed through WIDE to HV ON, SCAN switch
TPN-18, place POWER circuit breaker CB601 to ON
placed to OFF, FTC switch placed to OFF, and STC
(see Note above).
switch placed to OFF.
(8) On Pulse Generator O-1333/TPN-18
(5) Test equipment connected as shown in
master place SCAN MODE switch to SEARCH and
figure 339, except that only the oscilloscope channel A
SCAN switch to OFF.
10:1 prod connected to VIDEO testpoint TP2004 is used
(9) On Control-Indicator C-6988/TPN-18
in c below.
under alignment, place PPI CENTERING (NORM-
c. Procedure.
OFFSET) switch to OFFSET.
(1) On applicable Control-Indicator C-6988/
(10) Rotate overlay to position arrowhead
TPN-18, place FOCUS and VIDEO GAIN controls fully
on center grid line at 0 degree (top) so that gridlines are
ccw.
vertical.
(2) On mixer amplifier, rotate IFF VIDEO
(11) Adjust PPI CENTERING OFFSET
control R2201 fully ccw.
VERT and PPI CENTERING OFFSET HORIZ controls
(3) On oscilloscope, set SWEEP TIME
so that starting point of sweep is directly under center of
switch to 50 MICROSECONDS/CM, INTERNAL SWEEP
overlay.
MAGNIFIER switch to X10, and channel A SENSITIVITY
(12) Observe starting point of sweep as PPI
switch to .5 VOLTS/CM.
CENTERING OFFSET VERT control is rotated back and
(4) On mixer amplifier, adjust VIDEO BIAS
forth through its range. Starting point of sweep should
control R2027 until bright line at base of noise just fades
follow the center gridline on overlay. If starting point of
(decreases in brightness as minimum thresholding point
sweep does not follow center gridline on overlay, perform
is approached).
(13) through (15) below.
(5) Connect channel A 10:1 prod to
(13) At rear of applicable Control-Indicator
INTENS GATE testpoint TP2005.
C-6988/TPN-18, loosen two rotational locking screws in
(6) On oscilloscope, place controls to
mounting flange of deflection yoke assembly.
positions indicated in (a) through (k) below.
(14) Rotate deflection yoke assembly until
(a) POWER: ON.
start of sweep follows center gridline on overlay while
(b) SWEEP MODE: PRESET.
rotating PPI CENTERING OFFSET VERT control back
(c) TRIGGER SOURCE: EXT AC.
and forth through its range.
(d) HORIZONTAL DISPLAY: X1.
(15) Tighten two rotational locking screws in
(e) EXTERNAL VERNIER: CAL.
mounting flange of deflection yoke assembly, and
(f) SWEEP TIME MILLISECONDS
replace top access cover removed in (1) above.
CM: .1 (g) SWEEP TIME VERNIER: CAL.
3-49
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