TM 11-6625-586-45
(1) Voltage measurements. This equipment
a. Note the position of all leads be-
is transistorized. When measuring voltages, use
fore unsoldering a part. If a part
tape or sleeving (spaghetti) to insulate the en-
with multiple connections is unsol-
tire test prod, except for the extreme tip. A mo-
dered, such as a transformer, tag
mentary short can damage a transistor. Use the
each lead.
same or equivalent electronic multimeter speci-
b. Do not damage contacts or leads
fied in the voltage charts.
when pushing or pulling them out
(2) Intermittent troubles. In all the tests,
of the way.
the possibility of intermittent troubles should not
c. Do not use a large soldering iron
be overlooked. If present, this type of trouble
to solder small resistors, diodes,
often may be made to appear by tapping or jar-
transistors, or ceramic capacitors.
ring the equipment. Make a visual inspection of
Overheating may change the value
the wiring and connections to the unit. Check
of these parts.
that no external connection causes the trouble.
d. Do not allow solder drops to fall
Test wiring for loose connections by moving
into the chassis as this may cause
wires and components with an insulated tool.
short circuits.
(3) Resistor and capacitor color-code dia-
e. Make careful solder connections.
grams. Color-code diagrams for resistors, capac-
Poor solder joints are poor con-
itors, and diodes (figs. 6-5 and 6-6) provide
ductors and are difficult to locate.
pertinent resistance, voltage rating, and toler-
f. Reassemble all parts of the high
ance information.
frequency circuits in the exact po-
sition formerly occupied. A re-
2-3. Test Equipment Required
placed part with the same nomi-
The following chart lists the test equipment re-
nal electrical parameters but with
quired for troubleshooting the signal generator.
a different physical size from the
The chart also lists the associated technical man-
original part may cause problems
uals and the assigned common names. Observe
in a high frequency circuit. Fail-
Warning and Cautions following the chart.
ure to observe these precautions
may result in a decreased output
Technical manual
Common name
Test equipment
or in parasitic oscillations.
TM
11-6625-366-15
Multimeter
Multimeter TS-
g. Give particular attention to prop-
352B/U
er grounding. Use the same ground
TT
11-6625-1703-15 Oscilloscope
AN/USM281A
as in the original wiring.
Voltmeter, Elec-
TM 11-6625-524-14 VTVM
4. Do not make adjustments unless it
tronic AN/URM-
has been positively determined that
145
the fault is caused by a maladjust-
WARNING
ment.
Dangerous voltages are exposed when
5. Never connect test equipment (other
operating the signal generator removed
than multimeters and vtvm's) direct-
from its case.
ly to a transistor circuit. Use a cou-
CAUTIONS
pling capacitor.
6. M a k e test equipment connections
1. Do not tighten screws more than re-
with care so that short-circuits will
quired when assembling mechanical
not be caused by exposed test equip-
parts.
ment connectors. Use tape or sleev-
2. Always replace the lockwashers when
ing (spaghetti) to insulate the entire
assembling mechanical parts.
test prod or clip, except for the ex-
3. Careless reassembly of parts may
treme tip making contact with the
cause new faults. Observe the follow-
circuit under test.
ing:
Section Il. TROUBLESHOOTING GENERATOR, SIGNAL SG-297/U
to various test equipments. Ac power must be
2-4. Test Setup
connected to the signal generator for all dynamic
Bench tests of the signal generator require con-
servicing procedures.
nection to a 115- or 230-volt ac power source and
2-2
