ELECTRICAL UNIT INTERMEDIATE MAINTENANC
SECTION I TROUBLESHOOTIN
4-1. General Instructions.
a. Troubleshooting procedures are provided in logic tree format. They are correlated to power sup-
ply and DVM tests (para 4-40) and final test (para 4-42). Use the schematic diagrams (FO-1, fig 1-6
through 1-9, and FO-2) and the wiring diagram (FO-21) as aids in troubleshooting. For each failure that
can occur during the tests, there is a trouble symptom with a similar title. The troubleshooting is also
presented in the sequence as the tests. Find the troubleshooting paragraph which corresponds to the
test paragraph. Then use the logic tree to isolate the defective circuit or component.
b. During troubleshooting, observe the following precautions.
(1) Perform continuity and resistance checks with electrical power off.
(2) When measuring voltage, use tape or plastic sleeving (spaghetti) to insulate the entire test
probe, except for the extreme tip.
High voltage (115-volt 60 Hz ac) is used in this equipment. Death on
contact or serious injury can result if personnel do not observe safety
precautions. Be careful not to touch high voltage connections when
4-2. Test Equipment Required.
For test equipment required, see table 4-1.
Table 4-1. Equipment Required for Troubleshooting Electrical Unit
AC: 50 mV to 150V, 0.5%
DC: 10 mV to 50V, 0.1%
0.5 Hz to 1 KHz, 0.1%
Oscilloscope, Dual Trace
0 to 10 MHz, 1 us to 500 ms/div
5 mV to 20V/div
0-150 Vac, 1500 W
Test Aid, Locally Fabricated
13 Vac to 0-6 Vat, in-phase
or out-of-phase (fig. 4-1)
Load Resistor, 2000 Ohms, 1 Watt
Tool Kit TK- 101/G