7. Replacement Of Brushes
WARNING: USE ONLY B.F. GOODRICH BRUSHES. DO NOT SEPARATE UNITS WHEN REPLACING BRUSHES. FAILURE TO FOLLOW THESE INSTRUCTIONSMAY RESULT IN FAILURE OF THE DEICER UNIT.
NOTE: It is not necessary to remove the individual units from the modular brush assembly for brush replacement when this procedure is followed.
(a) Remove old brush. (1.) Remove screw securing terminal to housing base. Note brush identification A, B, or C. (2.) Remove terminal from brush lead and remove brush through brush opening of unit. (3.) Inspect inside of module unit to ensure no foreign material is present.
NOTE: If module unit housing is worn or damaged, replace the entire module.
(4.) Clean outside of brush opening to remove any carbon deposits.
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B. MaintenancePractices (continued)
7. ReplacementOf Brushes (continued)
(b)
Preparenew brush (see Figure 504). (1.) Slide tubing over brush lead so end of tubing almost contacts the brush. (2.) Form lead in an arc as shown.
(c)
Installbrush in module (see Figure 505). (1.) Insert lead into brush opening. Slide brush into base until lead protrudes through lead exit hole. (2.) Compress brush and pull lead to obtain maximum availablelength of lead outside module
base. (3.) Secure brush in compressed state using rudder band (see Figure 506).
(d)
Installterminal (see Figure 506). (1.) With brush compressed, slidetubing to within 3/16 inch of the end of the bare wire (as
shown).
(2.) Install ring terminal so the end of the insulating tubing is positioned insidethe insulated jacket of the terminal so no bare wire is exposed. (3.) Crimp terminal in place with recommended
crimpingdie and tool.
(e)Attach brush lead (see Figure 507). (1.) Replace screw and washer (and spacer if needed) as shown. (2.) Identify module unit A, B, or C (as required) with permanent ink or wire marker. (3.) Remove rubber band and carefully pull brush until all slack in lead is encased inside
module. (4.) Compress and release brush to ensure it does not bind or hang up inside module.
InsulatingTubing
Leadwire
Lead Exit Hole
ModuleBase
PreparingNew Brush Installing Brush Figure 504 Figure 505
RubberBandting)
Ring Terminal
AMP 32442)
InsulatingTubing Screw
InstallingTerminal AttachingBrush Lead Figure 506 Figure 507
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B. MaintenancePractices (continued)
8. AlignmentOf Brushes (refer to Figures 508 and 509)
NOTE: The brush alignment at installation must be checked any time the modular brush assembly is dismounted or brushes are replaced.
(a)
Note direction of slip ring rotation.
(b)
Place template against face of brush assembly.
(c)
Slide brush assembly forward until template meetsslip rings.
CAUTION: SLIDE LOADS ON BRUSHES SHOULD BE AVOIDED TO PREVENT BRUSH DAMAGE.
(d) Tightenbrush assembly and remove template.
section of parts catalog to order brush alignment
NOTE: Refer to miscellaneous template.
SlipRing Slip Ring Rotation Surface
Brush O O
Assembly
Template
ModularBrush Alignment Template
Figure 508
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PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
B. MaintenancePractices (continued)
8. AlignmentOf Brushes (referto Figures508 and 509) (continued)
100%OFBrush SlipRing
ContactsSlip Assembly Brush
Ring Surface Assembly
ProperRadialAlignment CenterBrushesOn Slip Rings Incorrect Radial Alignment
TheFullThicknessOf Each Brush FaceMust
Contact The Slip Ring Throughout360° Rotation
Slip Ring Rotation ResultsCausedBy ResultsCausedBy
Spring CockingAssemblyAt Allowing Too Great Of
Pressure TooGreatOf An Angle A DistanceBetween
On Brush BrushAssembly Brush Housing And
Slip Rings
CorrectFore & Aft Alignment IncorrectAlignment
ModularBrushAssemblyAdjustment
Figure509
9. BrushModuleReplacement
Measurethe brushes as shown in Figure 503. Replacebrushmodulesas follows:
CAUTION: BRUSH AND RING SERVICE LIFE MAY BE REDUCED IF OIL IS PRESENT ON BRUSH UNIT. REFER TO PRATT& WHITNEY PT6A-61 MAINTENANCE MANUAL FOR FIXING OIL LEAKS.
NOTE: Theentirebrush moduleunit should be replaced whenconsiderablewearof the housing is apparent.
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