Diode Replacement - Piper PA-24 Comanche Service Manual

PIPER COMANCHE SERVICE MANUAL
With the stator diticoMectH, check a
diode in the heat sink
by
connectina OIle of the
ohmmeter le-:ll to the h.at sink, IDd the other
ohmmeter lead to the diode lead, acd note tbe
raRdina (Fiaura
~20). Then
revene the ohm.
meter lead connectiou, aad note the re.iDa.
If both re-:linp are very low, or if both readillp
are very hip, the diode i. defective. A load
diode will live one low raadina ad one bilh
readiDa. Check the other two diodes in
the
heat
link in the IUle manner.
To cbeck a diode iaoWlted in the end
frame, COMect one of the oh. .eter leads to the
end frUle, and the other ohmmeter le.:1 to the
~iode
le.d (Fipre 9--20), and note the raRdin••
Then raverse tbe ohmmeter lead COCUIec:tiOftS,
and note the Nadial' If both raRdinls are very
low, or if both readin,1 are very hip, the diode
is defective. A looci diode will live one low
readinl and one hiah readma. Check tbe other
IIIGUIE '.20. CHECKING DIODES
two diod.. in the end frame in the salle mMner.
Tnt Lamp Method: An alternate method of cbeclci.nl the diod.. is to llIe a telt lamp of not
more than l2-volts in place of the ohmmeter.
CAUTION
Do not uae Uo.volt test lamps to cbeck diod...
With the stator disconnected, connect the test lamp leads
8CtQtIS
e-eh diode as previously
described first in one direction and then in the other.
If
the lamp
Upaa
in both checks, or faUs to
liaht in both checks. the diode is defective. When chec:kinl a IDOd diode,
the lamp will li&JIt in
only one of the two checks.
Special Tester Method: Special testers are available which operate without disconnectina
the stator. To ule these testers, foUow the tester manufacturer's recommend.tions.
9-50.
DIM. R.,I.u....
nt. To repl.c•• diode, u•• a suit.ble tool to support the end frame or
heat sink, and u•• an arbor prass or vise to push the diode out. Also us•• lpecial tool which fits
over the outer diode edle to push the diode in, and support the he.t sink and end frame with a
SUitable tool.
MOTI
Diode replecement tools are available from variou m.llufecturers
I\onnally supplyina tools and test equipment to the aviation in·
dllStry .
ELECTRICAL SYSTEM
ISSUED: 8/18/72
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