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ELECTRICAL
203
SERVICE
PROCEDURES
To correct generator troubles, proceed as outlined
hereafter.
The only repairs that may be carried out
by
Service Station personnel are:
- commutator Ie-turning;
- repairs of field winding connections being
broken, unsoldered or with damaged insulation.
Any other defective part must be replaced.
Commutator Re-Turning.
Disassemble generator.
The armature assembly must be placed on a
lathe and suitably centered. as it is not possible
to hold the armature shaft between lathe centers.
This centering must be perfect because commu-
tator Qut-oC-round must not exceed .0004" (0.01 rom).
After Ie-turning
I
undercut the
mica using cutter
Ap. 5015 (fig. 323).
Broken Field Winding, with Shorted
or Grounded Coils.
Repair only if trouble consists in unsoldered or
broken connections.
In all other cases replace
winding by a genuine one.
Do not attempt to build a new winding locally.
Field winding inspection may be carried out
using the bench for current feed and instrument
reading.
Fig. 323 • Undercutting mica between commutator bars using
fixture Ap. 5015,
1. Armature.• 2. Culter. - 3. Cutter arm actuating lever.
Fig. 324 - Testing generator armature for open coils.
1. Armature tester throw-in switch. - 2. Tester warning light.
3. Ammeter.• 4. Ammeter plug. - 5. Armature.• 6. Twin contact
insulated grip.
In correspondence with an open coli the ammeter reading will be zero.
Heat new winding to 122
0
F (50
0
C) before instal-
lation, to render it slightly flexible, thus facilitating
its
seating under pole shoes.
Pole shoes must be well set against frame and
their screws fully tightened, so as to restore original
air gap.
After reassembly, check that pole shoe inner
diameter is 2.2952" to 2.3012" (58.3 to 58.45 mm).
If
diameter departs from above figures, it is
an
indication that assembly is incorrect.
In
this case, the whole procedure must be re-
peated.
Never ream pole shoes.
Fig. 325 • Testing the armature on bench, using a lamina.
In correspondence with short-circuited coils the lamina will vibrate.
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