Section VI
Paragraphs 6-18 to 6-21
TABLE XIII DYNAMOTOR TROUBLE SHOOTING
OSCILLATOR. Unless it becomes necessary to move
(Cont)
the switch rotors while the oscillator is disassembled,
REMEDY
PROBABLE CAUSE
SYMPTOM
the oscillator can most easily be reassembled to the
slug rack by setting the MEGACYCLES control to the
frequency noted in paragraph 6-19, step e, above and
Noise in
Arcing at brushes,
Replace or
sliding the oscillator carefully hack into place.
signal
service
broken or cracked
generator
brushes.
brushes, brushes
sticking in holder.
output .
Unless care is exercised, the oscillator may
High commutator
Return to qual-
be reassembled to the slug rack with the switch
ified overhaul
bar, high mica be-
rotors 180 from their correct position. Refer
tween commutator
depot.
segments.
to figure 6-7 for relative positions of the slug
rack adapter and switch rotors for several dif-
Dirty commutator.
ferent frequencies.
Clean with cloth
saturated with
gasoline.
Vibration.
Bent shaft.
There are two switches in the oscillator. Both
Return to qual-
switch rotors must be lined up properly before
ified overhaul
inserting shaft, otherwise damage to the sec-
depot.
ond switch rotor will result.
Dynamotor mount-
Tighten mount-
ing not secure.
ing screws.
ADJUSTMENT. If the two set screws on the coarse
frequency oscillator shaft adapter ever become loos-
ened and the synchronization lost, it will be necessary
to follow the procedure below to restore the original
synchronization.
a. Remove rear access cover (10) and coarse fre-
quency oscillator crystal cover (11, figure 6-6).
LATOR. Should it become necessary to remove the
coarse frequency oscillator proceed as follows:
b. Pull out 9625.000 kc crystal, Y1528 and attach
an ohmmeter between the lower socket and ground as
a. Remove the top, bottom and rear covers from the
shown in figure 6-8.
r-f chassis.
C.
Set MEGACYCLES control to 135 mc.
b. Unsolder six leads (1, figure 6-5) connected to
the terminal strip on the side of the oscillator. Label
each lead as it is removed to insure proper replace-
d. Loosen and turn the shaft adapter at the rear of
ment.
the slug rack so that when viewed from the front of the
signal generator one set screw is pointing straight out
to the left and the other set screw is pointing straight
C . Remove three nuts (1, 2, 3, figure 6-6) which
up. This will closely approximate the 135 mc position.
fasten the oscillator to the rear of the slug rack.
e. Turn the adapter back and forth and note by the
d. Slide the oscillator carefully off the slug rack
ohmmeter reading the approximate points at which
shaft adapter (4, figure 6-6) and out through the open-
the coarse frequency oscillator switch no longer
ing in the rear of the r-f shield.
makes contact. These points will be evidenced by the
ohmmeter reading rising from 100,000 ohms to open
e. Carefully note, or record by sketching, the ori-
circuit.
entation of the Slots in the rotors of the two-section
wafer switch in the oscillator. Also note and record
f. Set adapter midway between these two end points
the setting of the MEGACYCLES control on the front
panel.
and tighten both set screws.
g. Replace crystal Y1528 and the crystal cover.
Connect power to the signal generator. Turn the
MEGACYCLES control from 135 to 108 and back to
Never loosen the two set screws on the coarse
135 checking the reading of the CARRIER meter at
frequency oscillator shaft adapter for any rea-
each frequency setting to make certain that normal
son other than replacement of the shaft or
r-f output is obtained on all channels regardless of
direction of approach.
adapter. If these screws should be loosened
accidentally or for the purpose of replacing a
damaged shaft or adapter follow the procedure
in paragraph 6-21 to restore the original ad-
h. If good switch contact is not obtained at all fre-
justment.
quencies, reset the MEGACYCLES control to 135 and
