MAINTENANCE OF GENERATOR ASSEMBLY
Section I. DESCRIPTION AND FUNCTION
Refer to Operator and Organizational Maintenance
Manual for description and function of the generator.
Section II. MAINTENANCE
8-2. GENERATOR MAINTENANCE.
a. Test (On Equipment) (see fgure 8-1 ). On generators equipped
with the Acoustic Suppression Kit (ASK), the ASK cover assembly
must be removed for inspection and repair and replaced at comple-
tion of task. Refer to Operator and Organizational Maintenance
Manual for removal and installation of ASK cover assembly.
(1) Isolate the trouble to generator or regulator.
Discomect the voltage regulator at the exciter (wires
P67C16 at TB3-5 and P60E16 at TB3-6). Connect a 12
volt battery in place of the regulator with the (+)
terminal to TB3-6 and (-) terminal to TB3-5. Run the
engine with the battery in place of the voltage regula-
tor. If there is output now, the voltage regulator is
bad. If there is no output, the main alternator is bad.
(2) Check generator operation. Run the set without
an external load, if the engine appears to be loaded
(dark smoke apparent) the generator may have a wind-
ing short to ground. If the engine does not seem to be
loaded, there may be open windings.
(3) Testing Diodes (see figure 8-1). A shorted or
open diode in the rotating rectifier assembly can
cause bad generator operation. This is evident by
failure of the generator terminal voltage to build up
to rated value or a terminal voltage that is too low.
When these symptoms are noticed, and the more ob-
vious sources of trouble, (1) and (2) above have been
eliminated, check the individual diodes of the rotating
rectifier assembly as follows:
(a) Loosen four screws (5) and rotate bell
cover (7) until it can be removed over screw heads.
(b) Disconnect each diode (42) by removing
nuts and washers (40 and 41).
(c) Use an ohmmeter to measure the resis-
tance between the terminal end and the threaded base
(heat sink) end of the diode. Reverse ohmmeter leads
and repeat the resistance measurement. A diode in
good condition will have a very high resistance for
one measurement and a resistance near zero when
ohmmeter probes are reversed, Failure to obtain these two
extremes in resistance measurement indicatas a defective diode
that should be removed and replaced.
Be sure points of ohmmeter probes are suf-
ficiently long and sharp to penetrate any in-
sulating varnish on diode terminals.
(4) Replacing Diodes. Diodes of the rotating rec-
tifier assembly which are found to be defective or in
questionable condition can be removed and replaced as
(a) Unsolder wires from diodes.
(b) Install new diode and attaching hardware.
Tighten nut (40, figure 8-1) only finger tight.
(C) Using a 25 to 40 watt soldering iron, solder
leadwires to terminal of replaced diode. To protect
diode from damage due to heat caused by soldering,
hold diode terminal with needle nose pliers as a heat
sink and use a low melting point solder.
(d) Allow each diode to cool after soldering.
Tighten diode mounting nut (40) to torque of 30 inch-
(e) Install end bell cover (7).
(f) Tighten bolts (5).
(5) Resistance. Use resistance check to locate
b. Removal. Refer to paragraph 2-10 for generator