TM 11-6625-828-12
Item
NO.
Trouble symptom
Probable trouble
Checks and corrective measures
15
% M meter needle does not
Defective electron tube V105, filter Z102,
Refer to higher category of maintenance.
align with the red line on
capacitor C124, resistors R145, R149,
the upper scale.
R155, R156, or R158, MODULATION
switch S102G, or 90~ MOD control
R130.
16
% M meter needle does not align Defective filter Z103, resistors R147,
Refer to higher category of maintenance for
with the red line on the upper
R154, or R157, or 150~ MOD control
repair.
scale.
R144.
17
% M meter needle does not indi- Defective 1000~ MOD control R163 ------
Refer to higher category of maintenan ce for
cate 100 to 0.
repair.
18
% M meter needle does not
Defective electron tubes V106 or V107
Refer to higher category of maintenance.
Pulse.
other 1,0000-cycle oscillator com-
ponents, or IDENTIFIER switch S104.
from the power source. Use Multimeter AN/USM-223 to
4-12. Power Troubleshooting
perform a continuity check between terminals on the
When it is apparent that power is not being applied to
connectors of Power Cable Assembly CX-337/U.
the SG-66B/ARM-5, check to see if power is available
Figure 4-2. Deleted
(1) Unscrew the crystal cover cap (fig. 3-1) and
4-13. Repairs
remove it to expose the two crystals.
a. Replacement of Indicator Lamp.
(2) Grasp the crystal to be replaced between the
(1) Turn the indicator lens cap (fig.
thumb and forefinger and work the crystal out of its
counterclockwise and remove it to expose the defective
socket.
lamp.
CAUTION
(2) Remove the defective lamp by pressing it in and
turning counterclockwise.
Do not use pliers or similar metal-
(3) Replace the defective lamp with a new one.
jawed tools to remove crystals.
Push the lamp in and turn it clockwise to lock it.
(3) Seat the replacement crystal securely in its
b. Replacement of Fuses. The SG-66B/ARM-5
socket and screw on the crystal cover cap.
contains two active and two spare 3-ampere fuses
NOTE
located in the lower left portion of the front panel (fig. 3-
If the replacement crystal is for a
To replace a fuse, turn the fuse-holder cap
frequency different from that shown
counterclockwise, remove the cap, and extract the
by the corresponding front panel tab,
defective fuse. Install a new fuse of the proper rating
replace the tab with one showing the
and replace the fuseholder cap, locking it in place with a
new crystal frequency.
clockwise turn.
c. Replacement of Crystals.
Figure 4-3. Deleted
Change 1 4-6
