Sections V-VI
b. Remove the top and bottom covers from the r-f
chassis and clean the chassis with a soft brush or
vacuum cleaner.
c. Check the signal generator and dynamotor for
mechanical damage, loose parts, and signs of over-
heating and corrosion.
d. Check the dynamotor brushes for a minimum
length of 1/4 inch. Replace tf necessary. See Section
VI, paragraph 6-32.
e. Check the dynamotor commutator for evidences
of grooving or pitting. Dress if necessary. See Sec-
tion VI, paragraph 6-31.
f. Lubricate equipment as given in paragraph 5-1'7.
g. Replace chassis covers and secure the signal
generator in its case.
h . Perform the intermediate inspection given in
5-22. SPECIAL INSPECTION. After each 2000-hour
period of operation, replace all tubes in the equip-
ment and perform the major inspection given in para-
graph 5-21.
SECTION VI
FIELD AND FASRON MAINTENANCE
6-2. The minimum performance standards for Signal
When checking tube filaments, only apply
Generator, SG-13/ARN are given in Section V, para-
enough voltage with SET LINE TO 2lV control
graph 5-1 through 5-8.
to note whether tube filaments are lit. Do not
remove tubes when the power is on. Tubes
are in series-parallel arrangements and with-
drawing one may damage others in the circuit.
chassis or particular circuit, refer to Section V,
a. If only V1501 and V1509 are lit, check filament
perform the following checks and make voltage and
continuity of V1508. If the V1508 filament is good,
resistance measurements to locate the faulty compo-
voltage dropping resister R1555 may be open.
nent. Tube locations are shown in figure 5-3.
b. If only V1502 and V1507 are out, check these two
tubes.
c. If only V1503 and V1504 are out, check these
inoperative check all its tubes. With the signal gen-
tubes.
erator removed from its case and its top cover re-
moved, apply power to the signal generator. Note
d. If only V1505 and V1506 are out, check these
whether all tubes light. Because of the series-parallel
tubes.
arrangement of tube filaments (figure 4-29), a burned
out heater will open the heater circuit for other tubes.
e. If only V1501 and V1509 are out, check these two
Tube checking can be simplified by proceeding as
tubes. If both V1501 and V1509 are good, voltage
follows:
dropping resistor R1557 may be open.
