overheating and for cracks, breaks, defective
threads, and other damage.
(3) Inspect the variable resistor for proper
operation and for proper resistance. Resistance
should vary smoothly from 0 to 1,500 ohms when
the unit is turned through its range. Replace a
defective variable resistor.
(4) Inspect wire leads for breaks, poor connet-
tions at the terminals and for broken or frayed
insulation. Replace defective wire leads.
(5) Inspect the voltage regulator for cracks,
breaks, signs of overheating, and other damage.
Replace a defective voltage regulator.
Apply one coat of varnish meeting specification
MIL-V173 to the exposed circuit ,area of the
c. Assembly and Installation.
(1) Refer to figure 8-2 and assemble thc control box.
(2) After assembly of the cotrol box, apply
one coat of clear varnish meeting specification
MIL-V-173, Type II.
(3) Install the control box (pare 6-3).
d. Test. Test the DC control box components as
(1) Voltage regulator.
(a) Disconnect load cabics and start generator set.
(b) Trip the circuit breaker to ON position,
and observe reading on set voltmeter.
(c) Using a multimeter, check the voltage
across the output terminals to verify the reading
on the set voltmeter. If the voltage is low and
adjustment of the variable resistor will not correct
the deficiency, check the exciter voltage across
terminals 5 and 6 of the voltage regulator. This
voltage will vary but should be about 25 volts. If
no voltage appears on the regular terminals, the
voltage regulator is defective and should be replaced.
(d) If voltage across regulalor terminals 5
and 6 is satisfactory, stop the genrator set, at
tach the load cables, and restart the set.
(e) If voltage is still not satisfactory, replace
the voltage regulator and repeat steps (a) thru (d)
(2) Circuit breaker.
(a) Attach a variable load to the output terminals
and start the generator.
(b) Move circuit breaker to ON position and
observe the load meter and volumeter. Reading
should be 28 V at 100% load.
(c) Adjust the variable load until a reading
of 125% is obtained on the load meter. The circuit
is designed to trip at 125% maximum load.
(d) If the circuit breaker trips below 125%
maximum load, replace it.
(3) Capacitor (noise suppression).
The only accurate way to test a capacitor is by
putting it on a capacitor tester. However, you can
tell if a capacitor is working by the following
(a) Stop the generator set and disconnect
the lead-in terminal to the capacitor.
(b) With multimeter on the high scale ohms setting,
touch the test probes to the input learning and the
capacitor metal case, then reverse the probes. The
multimeter will give a momentary reading then fall back
(c) If this reading does not occur, then replacc the
(4) Variable resistor (DC).
(a) Stop generator set and disconnect terminal 1 on
the voltage regulator.
(b) Insert multimeter probes across the two outside
connected terminals of the variable resistor. With the
variable resistor in the full counterclockwise position,
slowly turn the control knob to the full clockwise
position. This reading should move smoothly from 0 to
1500 ohms ± 20% as the variable resistor is rotated to
the full clockwise position.