Piper Comanche PA-24 Service Manual page 671

,
PIPER COMANCHE SERVICE ,.ANUAL
9-14. Di .......
~ly.
lI.p.ir A.eI 1I .... _bly. NOflllally. disassembly sbOllld proceed ollly so far
as is neceslary to ... ke rep.ir or replacement of the defeetive parts. For example. the field coils
should
be
checked for opens. shorts. or IIfOUIlds before beina removed from the field fr.me: they
sbould
be
removed only if they require repair or replace .. ""t.
9-15. Fi.ld Coil 110 .....
1. Field coils can be removed from the field &ame IDost euily
by
use
of • pole shoe screw driver. It is a1ao advisable to un a pole sboe spreader, silica this pre .....
ts
distortion d the field frame. The pole sboe sere ... driver pefIIlits easy looe .... ina .nd removal of
the pole sboe screws so th.t the pole shoes Md field coils can be t.k .... OUt of the field fr ... e.
The pole sLoe screw driver .nd spre.der should be used "" reassembly of the field fr ... e. Careful
reusembly is Ileceasary to
preve~t
sbartina or """"dina of tbe field coils as the pole sboes are
ti&bt .... ed into place.
9-16. 1 •• pacti.n ..... eI lI.poir Of Port •.
a. The arm.ture or field should not be cleMed " My decre_ina tMk or
by
use of de"easina
compounds, since this might d .... '" insuJatiOll s, at. shurt or IIfOUIld would subsequently de-
velop. Sealed bail bearinas do not require cleuin, or relubric.tioa. Other leneratar parts sbould
be
cleaned and carefully inspected for wear oad other damsle. Ally defective parts should
be
repaired or replaced. On reassembly .11 soldered electrical conaeetions should
be made with
rosin flux. Acid flu.x must a.ever be used on electrical ccmnltCtioas.
9-17. Fi.ld Coil.
L
The field coils sbould be cbecked for &fOunds, opens or shorra as already e""lained in
para".ph 9-10.
b. Grounded field coils may
sOIDetimes
be repaired
by
removiJll them so they can
be
reinsu·
leted. Care must be used to avoid excessive buIltin •••• hen applying new insulation. 'Jiince this
might cause the pole shoe to cut through and cause another ground when the coils are reinstalled.
c. Usually, if a field coil is opea or shorted intemaUy it will require replacement. since lt is
difficult to repair such a defect.
d. To remove or replace field coils in the field frame, the use of a pole shoe spreader and
screw driver is recommended.
9-18.
Armatur. Se,..,ic ••
•• The arm.mre should be cheeked for opens, sborts ... d "ounds .s explained in following
parap1lphs. If the armature com.mutator is wom, dirty, out of roun.d, or ha. high mica, the armature
should
be
put
in
a lathe so the commutator can
be
turned down aDd the mica un.derti)Jt. The mica
should
be
undercut
1/32
of
OIl
inch and tbe slots cleaned out carefully to remove OIly trace of dirt
or copper dust.
As
a fin.l step in this procedure, the commutator should be sanded ligbtly with
No. 00 s""dpaper to re.,ove ""y sli,ht burrs that micht
be
left .s a result of the undercutting
procedure.
b. Open circuited. armatures can often be save-d .he the open is obvious and repairable. The
most likely place an open will occur is at tbe commutator riser bars: this usually results Crom
overloading of the generator, which causes ovemeatinc and meltiag of the solder. Repair can be
effected
by
reseldering the leads in the riser bars (using rosin. fll.lx) and tuming down the com·
mutator
In
a lathe to remove the burned spot and then undercutting the mica as explained in the
previous paragraph.
In
some heavy-duty armatures the leads are welded into the riser bars, and
these cannot. of course,
be
repaired
by
resolderine.
3 A19
ELECTRICAL SYS'tEM
ISSUED:
8/18172