TM 11-6625-255-14/TO 33A113-170-1
tion method.
to the dc resistance of transformers and coils,
sockets (fig. 7-7) and other related points.
c. If voltage readings are abnormal, take
to trace circuits and to isolate the faulty part.
resistance readings (figs. 7-7 and 7-8). Refer also
SECTION III. MAINTENANCE OF SPECTRUM ANALYZER
710. General Parts Replacement Tech-
that attaches rear drive cable 0 20 to groove
pulley 0 14 and the screw that attaches front drive
niques
cable 0 21 to flat pulley 0 13. Remove the old drive
NOTE
cables and discard them.
Several of the spectrum analyzer parts
(3) Cut a piece of cable 11 inches long. Place
have smaller tolerances than those used
clamp E60 over one end of the cable. Form a loop
in most radio equipments. Resistors R1,
around the mounting screw in the end of the cable
R2, R26, R27, R28, R29, R30, R31,
and insert it back through the clamp. Slide the
R39, R47 and R91, used in the Wien
clamp tightly against the screw with the end of
bridge, are precision-selected at the
the cable extending approximately one-eighth of
factory as part of switch assembly S3. If
an inch. Place the clamp on a bench and tap the
these parts require replacement, replace
clamp. Insert the free end of the cable through the
complete switch assembly S3. Resistors
hole in the large groove section of cone pulley 0
R58 and R88 (R92 through R98) are part
19. Pull the cable through far enough to form a
of switch assembly S6 and have been
loop and install clamp E60 as described above.
designed specifically
for Spectrum
(4) Cut a piece of cable 15 inches long, Form
Analyzer TS-723(*)/U. If either of
a loop in one end as described in (3) above. Insert
these resistors becomes defective, re-
the free end of the cable through the hole in the
place complete switch assembly S6.
side of cone pulley 0 19 associated with the small
Resistors R77, R78, and R90 are close
section of the pulley. Form a loop in the cable as
tolerance resistors and must be selected
described in (3) above.
during replacement as described in
(5) Attach drive cables 0 20 and 0 21 to cone
pulley 0 19; use the attaching screws,
(6) Loosen the setscrews in drive shaft collar
are easy to reach and replace if found faulty. The
0 6. Seat rear drive cable 0 20 in the groove of the
sockets, filter capacitors, filter choke, and trans-
large section of cone pulley 0 9.
former are securely mounted to the chassis with
b. All front panel knobs are held with Allen-
hexagonal nuts, machine screws, or rivets.
head setscrews. When removing a knob, make a
b. In the TS-723A/U to reach capacitor C6,
note of the position of the pointer and shaft and
switch S2, and variable resistor R4, remove the
replace the knob under the same conditions.
four Phillips-head screws that attach the front
712. Disassembly and Reassembly of Ca-
panel. Remove the four Phillips-head screws that
attach the capacitor drive assembly to the front
pacitor Drive Assembly
panel. Pull the front panel away from the capaci-
CAUTION
tor drive assembly.
Do not dissemble the capacitor drive
c. If any of the switches requires replacement,
assembly unless it is absolutely
carefully mark the wires connected to the switch
necessary; it is very difficult to recali-
wafers with tags to avoid disconnection when the
brate. If it is necessary to repair the ca-
new switch is installed. Follow this practice
pacitor drive assembly, disassemble it
whenever replacement requires disconnecting
only as far as necessary to repair the de-
several wires.
fective part.
711.
Replacement of Capacitor Drive
a. Disassembly. Disassemble the capacitor
Cables
drive assembly (fig, 7-10) as follows:
(1) Loosen the setscrew that attaches each
(1) Remove the top cover.
FREQUENCY dial knob, and remove the two
(2) Cut the old cables. Remove the screw
FREQUENCY dial knobs. Removal of the lower
that attaches rear drive cable 0 20 to cone pulley 0
FREQUENCY tuning dial knob releases disk
19. Remove the screw that attaches front drive
spring A3.
cable 0 21 to cone pulley 0 19. Remove the screw
(2) Remove the four No. 10-32 Phillips-head
7-10
