Onan UF Series Instruction Manual And Parts Catalog page 71

M A T N T F . N A N H F . 13
factory and is identified by a painted or chisel mark on the outer edge of
the brush rig and must align with the edge of the end bell where the
brush rig is mounted.
As long as the original brush rig and armature are continued in service,
these alignment marks must be observed.
MAJOR GENERATOR REPAIR. - Consult a competent mechanic or elec-
trician, familiar with a. c. generators,
to locate any faulty windings and to perform any necessary major re-
pair. Several tests for open or grounded circuits can be made without
disassembling the generator. Before making tests, and before disas-
sembling the generator, lift the brushes away from contact. After com-
pleting the maintenance, return the brushes to their operating position.
DISASSEMBLY. - If it should become necessary to disassemble the gen-
erator, lift all brushes from contact. Tag all leads
which are disconnected, to insure correct replacement when the genera-
tor is reassembled.
When reassembling be sure the bearing stop clip is in place on the bear-
ing opposite the drive end. Avoid possible damage to parts through
careless disassembly and reassembly. Most other assembly procedures
are self-evident.
ARMATURE GROUNDED. - See that all brushes are lifted out of their
holders. Use a continuity type test lamp
set. Place one test prod on the commutator, and the other prod on a
bare clean part of the generator frame or armature shaft. The prods
must make good electrical contact. The test set lamp should not light.
If it does light up, the armature is grounded. Test the slip rings in the
same manner. If the armature tests grounded, replace with a new one.
TESTING THE ARMATURE FOR AN OPEN CIRCUIT. - The AC winding
of an alternat-
ing current generator may be tested for an open circuit by use of the
test lamp set. Place one test prod on one slip ring, and the other test
prod on a second ring. The test lamp should light. If it does not light,
an open circuit is present. If there are three or four rings, test between
each two in the same manner. Install a new armature if an open circuit
is present.
To test the direct current winding of an armature for an open circuit,
the use of an armature growler is necessary. Most electrical repair
shops have such equipment. It will be necessary to remove the arma-
ture for testing. Proceed as follows.
a. Place the armature in the growler which is connected to alternating
current. Rub a smooth steel blade (back edge of a hacksaw blade)