C2, TM 11-6625-623-45
Section I. GENERAL TROUBLESHOOTING TECHNIQUES
Warning: When servicing the function test set, be careful when working with the 115-volt,
100-CPS, ac line voltage. Disconnect the power cable from the power source when making in-
ternal resistance measurements.
(2) Measurement chart. If no symptoms
21. General Instructions
are known, perform the checks given
Troubleshooting at general support and de-
in the measurement chart (para 2-4).
p o t maintenance level includes all the tech-
(3) Troubleshooting chart. The symp-
niques o u t l i n e d for organizational mainte-
toms and procedures listed in the
nance and any special or additional techniques
troubleshooting chart (para 2-5) will
r e q u i r e d to isolate a defective part. The gen-
aid in isolating the trouble to a spe-
e r a l support and depot maintenance proce-
cific circuit or component.
dures are not complete in themselves but sup-
(4) Intermittent troubles. In all test, the
p l e m e n t the maintenance and repair proce-
possibility of intermittent troubles
d u r e s described in TM 11662562312. The
should not be overlooked.
s y s t e m a t i c troubleshooting procedure, which
ent, this type of trouble often may be
begins with the maintenance and repair proce-
made to appear by tapping or jarring
d u r e s that can be performed at an organiza-
the equipment. C h e c k the wiring
t i o n a l level, must be completed by additional
and cable connections.
localizing and isolating techniques.
c. Isolation. Once the faulty circuit or sec-
tion of the circuit is located, the faulty compo-
2-2. Organization of Troubleshooting
nent is located by voltage and/or resistance
measurements. Use the voltage and resistance
diagram (fig. 2-4) to find normal readings,
a. General. The first procedure in servicing
and compare them with readings taken. Use
a defective function test set is to localize the
resistor and capacitor color codes (fig. 49 and
f a u l t . Localizing means tracing the fault to a
410) to find the value of components.
circuit. The second procedure is to isolate the
f a u l t . isolation means tracing the fault to a
defective part responsible for the abnormal
2-3. Test Equipment Required
The following test equipment is required
b. Localization. The first procedure in trac-
for troubleshooting the function test set:
ing trouble is to locate the circuit at fault by
a. Multimeter ME26B/U (multimeter),
the following methods:
TM 11662520012, or equivalent.
(1) Visual inspection. The purpose of
(differential voltmeter), TM 11-6625-438
visual inspection is to locate faults
10, or equivalent.
without performing tests or measure-
c. Power Supply PP-351/U (dc power s u p -
ments. Some faults, such as burned-
ply), TM 115121, or equivalent.
out resistors, can be located by sight.
The trouble, therefore, can be im-
Voltage supply must be adjustable to two-deci-
mal place accuracy.