TM 11-6625-1633-45
above) the tracking subassembly can be disassembled.
NOTE
Refer to figures 3-5 and 3-7, and proceed as follows:
Make sure to connect the proper plugs and
(1) Disconnect connectors P3 from coaxial con-
jacks when replacing the terminal boards.
nector A4P1 and coaxial connector P4 from jack A4J3.
(2) Remove the mounting screws and nuts and lift
4-4.
Removal and Replacement of Trac k-
the tracking assembly partially away from the rf oscil-
ing Potentiometers A4R20 and A4R23
lator section.
NOTE
a. Remove a tracking potentiometer as follows:
Perform the adjustment procedures given in
(1) Remove the rf oscillator section and the
tracking subassembly ( para 4-2 ).
component is in the modulation tracking cir-
(2) Carefully sketch or tag the connections to the
cuit or the alignment procedure in paragraph
potentiometer being replaced and unsolder the leads.
(3) Loosen the associated driver-gear set screws.
ler tracking circuit.
If necessary, rotate the center frequency selector hand-
wheel until the set screws are accessible.
4-3. Removal and Replacement of Terminal
(4) Rotate the center frequency selector hand-
Boards
wheel until the mounting screws on potentiometer
A4R20 or the one-half inch mounting nut on potenti-
ometer A4R23 are accessible.
(5) Remove the mounting hardware and pull the
a. The AN/URM-149 contains plug-in terminal
potentiometer away from the potentiometer plate assem-
boards TB2-A1, TB3-A2, and TB4-A3 and fixed termi-
bly.
nal board TB1. Terminal board TB1 is bolted to the
main chassis and should not be removed. The plug-in
b. Replace the tracking potentiometer as follows:
terminal boards can be removed from replacement or
(1) Mount the potentiometer in the same manner
servicing by disconnecting the cable connectors, un-
as the original.
locking the two cam locks and lifting the boards straight
up
.
Figure 4-1. Tracking potentiometers A4R20 and A4R23, mounting details.
4-2
