TM 11-6625-828-45
that secures the MC selector knob to the RI drive shaft.
(1) Secure cover MP137 with six screws H143
(3) Unscrew and remove the crystal cove and
and lockwashers H142.
remove the two crystals from the front pane (4)
(2) Replace connector J102, R190, and L-
Disconnect the RF cable at the RI unit.
115, and secure-with lockwasher H134 and nut.
(5) With a free hand, support the RF unit and
Solder the lead of R190 to connector J102 (fig. 3-5).
then, from the front panel, remove the four knurled nuts,
(3) Install the tube deck in RF unit housing
the MC selector switch shaft nut and the nut from the
MP154 and secure with hexagonal nuts H138.
crystal housing.
(4) On the inside of RF unit A125, solder the
(6) Tag and unsolder the connections to
leads of chokes L116, L119, Ll11, and L110 to terminal
feedthrough capacitors C134, C157, C155, an C133
board TB101.
located on the side of Z104 (fig. 3-4).
(5) Replace washer H137 on rotor assembly
(7) Remove the RF unit from the equipment.
H109.
b. After the RF unit has been removed, the unit can
(6) Replace the two setscrews H136 on the
be disassembled. Refer to figure 3-4 and proceed as
side of rotor assembly H109. Insert shaft MP144.
follows:
Tighten setscrews H136.
(1) Remove three screws H135 and lift out
(7)Insert rotor assembly H109 and secure with three
rotor assembly A109.
screws H135.
(2) Remove shaft MP144 by removing two
d. Replace the RF unit as follows:
setscrews H136 from the side of rotor assemble A109.
(1) Place the RF unit near its proper position
Two protective disks MP141 may be left in the rotor
so that the connections to feedthrough capacitors C134,
body.
C157, C155, and C133 can be soldered. Solder the
(3) Lift off washer H137.
connections to C134, C157, C155, and C133.
(4) From inside the RF unit, at terming board
(2)With a free hand, support the RF unit in its proper
TB101, unsolder the leads of four choke L111, L119,
position on the back of the front panel. On the front
L116, and L110 (fig. 3-5). Carefully straighten the other
panel, replace the nut in the crystal housing, the nut on
leads so that they do not interfere with the future removal
the MC selector switch, and the four knurled nuts.
of the tube deck.
Tighten all nuts alternately until the RF unit is secured
properly.
CAUTION
(3) Connect the RF cable (fig. 3-1) to the RF
In the following procedures be
unit.
careful not to bend or distort L115
(4) On the front panel, replace the two
and L112.
crystals and the crystal cover.
(5) Unsolder the connecting lead of R19 from
(5) On the front panel, replace the MC
J102 (fig. 3-4). Loosen and remove the nut, lockwasher
selector knob on the RF drive shaft and insert "the
H134, coil L115, and resistor R190. Take out connector
setscrew. Tighten the setscrew.
J102.
(6) Use a 5/i,-inch open-end or hexagon
3-5.
Removal and Replacement of RF Attenuator
wrench to loosen and remove four hexagonal nuts H138
Assembly
from RF unit housing MP154. Care fully remove the tube
RF attenuator assembly Z105 is mounted behind the
deck.
front panel above and below the main chassis (fig. 3-1).
(7) To remove cover MP137, loosen and
a. To remove the RF attenuator assembly, proceed
remove six screws H143 and lockwashers H142 Lift the
with (1) through (8) below.
cover up and slightly to the side when removing.
(1) Place Test Set, Radio AN/ARM-SA (minus
(8) The remaining parts of Z104 (fig. 3-4) may
cabinet) -on a work bench so that the front panel faces
be removed by.
using standard maintenance
the front edge of the workbench. Rotate the test set 90
procedures. Refer to the RF unit wiring diagram (fig. 3-
from right to left. The above procedure should provide
5).
access to RF
c. Reassemble the RF unit as follows:
3-5
