(d)
Turn on battery master switch and turn selectorswitch (L or R) for the unit being tested to the STARTposition.
(e)
Using a voltmeter, attach positive leadto the electrical leadremovedfrom terminal stud B+ on starter generator and the othervoltmeterleadto airframe ground. Voltmetershouldread the batteryvoltageof 24 volts.
(f)
Turn battery master switch off.
(g)
Disconnectthe voltmeter positivelead from wire removed from starter generator terminalstud B+.
(h)
Connectelectricallead previously removedto B+ terminal stud on starter generator.
9. Generator Brush Inspection
Generatorbrush inspection is recommended at 100 hour intervals. By means of the diagonalwear
grooveon the side of each brush,which shows 100% useful life when new, the percentage of
remainingusefullife is easily estimatedat each inspection. Inspectgeneratorbrushesas follows
to determinecontinued airworthiness:
(a)
Removebrush cover fromunit.
(b)
Removescrewssecuringbrushleads to brush holders. With a stiff wire hook, lift springs from brushesand removebrushes.
NOTE: If brusheswill be reused, mark each brushto allow that the brush will be installedinto brush holder that it was removed from.
(c)
Determineremaininglifeof each brush (referto Figure 601). If any one brush is estimated to be worn out before the nextinspectionor overhaul, replaceall brushes.
(d)
After inspection,replace brush cover. Ensure that cover is seated in housing recess and that exhaustair holesare located adjacent to terminalblock.
(e)
Installgenerator on aircraft.
(f)
After inspection,replacebrush cover. Ensurethat cover is seated in housing recessand that exhaustair holes are located adjacent to terminal block.
(g)
Installgeneratoron aircraft.
NOTE: Instant filming brusheswhich do not have cores or visible particles are identified by markingI/F, in addition to any grade numbersand date code letters.
NOTE: If new brushes have been installed, it is not necessary to conduct seating or run-in operationsdue to the ability of instant-filmingbrushesto carry full starting and generatingcurrentswithoutsuch run-in. If the specified brushis NOT one of these types, the unit must be returned to an overhaul shop for brush replacement, run-in, and test.
EFFECTIVITY:
PAGE8 040-999
Jan10/9024 3000
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. DC Generation (continued)
WEAR 1/4 LIFE GROOVE
1/2LIFE REMAINING REMAINING NEW BRUSH
Brush Wear Stages
Figure 601
SOLID STYLE
SPLIT STYLE
CORE TYPE RANDOMPARTICLE
ALTITUDETREATMENT ALTITUDETREATMENT
Instant Filming Brushes
Figure 602
EFFECTIVITY:
040-999
24-30-00 Jan 10/90 9
PAGE
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. DC Generation (continued)
Brush must be installed with top bevel as shown for the clockwise armature rotation indicated. (For reverse rotation units, top bevel will be opposite to that shown.
RECONNECTNEGATIVE FIELD LEAD
LAY BRUSH LEADS OVER BRUSH SPRING CLIPS
CorrectPositionof Brushes, Leads,and Springs
Figure 603
EFFECTIVITY:
PAGE10 24-30-00 040-999
Jan 10/90 "
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. DC Generation (continued)
10. Cleaning Generator (Assembled)
(a)
Remove generator from aircraft.
(b)
Remove brush inspection cover. Do not remove brushes during internal cleaning and resistance check procedures.
(c)
Internal cleaning:
WARNING: WHILE USING COMPRESSED AIR, WEAR GOGGLES OR FACE SHIELD TO PROTECT EYES. DO NOT AIM AIR JET AT EXPOSED SKIN. USE A DUST FILTER RESPIRATOR.
CAUTION: TO PREVENT DAMAGE TO BEARING SEALS AND TO AVOID FORCING CONTAMINANTS INTO BEARINGS, DO NOT AIM AIR JET AT BEARINGS
(1.) Remove carbon and copper dust from armature and stator windings using a low pressure (40 psi) air supply and nozzle. Start at the drive end of unit and work toward the brushes and commutator area.
WARNING: STODDARD SOLVENT IS TOXIC AND COMBUSTIBLE. DO NOT BREATHE VAPORS. USE IN WELL VENTILATED AREA FREE FROM SPARKS, FLAME, AND HOT SURFACES. WEAR SPLASH GOGGLES, SOLVENT RESISTANT GLOVES, AND OTHER PROTECTIVE GEAR. IN CASE OF SKIN CONTACT, WASH WITH SOAP AND WATER; IN CASE OF EYE CONTACT, FLUSH EYES WITH WATER AND SEEK MEDICAL ATTENTION.
CAUTION: DO NOT USE LUBRICANTS OR UNAUTHORIZED SOLVENTS, WHICH CAN REDUCE BRUSH LIFE.
(2.) Inspect interior of unit for oil and other contaminants. Wipe contaminants with clean cloth moistened with Stoddard solvent (Federal Specification P-D-680, Type 1).
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