Onan MJA Series Service Manual page 99

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Ii
REVOLVING FIELD
G.ENERATOR
. r ightsideo.f the plate and swing
the assembly Qutward. Tore­
move the brush holders, unscrew
the 4 machine screws on the end­
bell near the ballbearing..Re ­
place the brushes when they wear
to about 5/16" long. Don't use a
substitute brush that mayJook
identical. It might have entire ­
ly different electrical character­
istics.
4.2.2 GENERATOR BEARING. ­
The generator bearing is pre­
lubricated for life and sealed.
It
r.equires no servicing.
4.2.3 EXCITER. -Exceptfor FIG 4.H -REMOVING BRUSHES
the 02SX the exciter contains no
moving parts. PeriOdically blowout any dust and make certain that all
components and connections are. secure.
A build-up relay was used on the 02SX models. .Early models had Qpen
relays and later model relays were enclosed in metal shields. The r.e ­
lay contacts should be cleaned regularly. Carefully wipe the relay con­
tacts with paper to remove any non-conducting'film or dirt.
4.2.4 COLLECTORRINGS.- Thecollector rings must be clean and
free of scratches, burrs and marks.
If
necessary, use no. 00 sand­
paper to clean the surface. Never use emery cloth or other conducting
abrasives.
4.3 TESTING
AND
REPAIR
If repair work is necessary on the generator, it should be performed by
a competent electrician who is familiar with operation of electric gener ­
ating~quipment.
4.3.1 TROUBLE-SHOOTING. - In the event of abnormal generator out ­
put voltage, observe the folloT,ving procedures.
4.3.1.1 No Voltage Build Up. - First remove the exciter cover and
with the plant running, operate the residual reset button on the Magne­
citer. On the 02SX exciter, the build-up relay automatically performs
this function. Check its operation and contact s.
NOTE: Early04SX and 06SX models had no reset button. On these mod ­
els place jumpers momentarily from G1 to G20f each reactor
simultaneously with the plant running.