Piper PA-34-200T Seneca II Service Manual Download

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PIPER SENECA II SERVICE MANUAL

14-14. INDIVIDUAL BRUSH REPLACEMENT.

Remove brush retainer assembly per Paragraph 14-13.

Mark receptacle flange and brush retainer block to permit reinstallation in the same position.

Unsolder brush leads from receptacle pins and discard old brushes and springs.

Install insulating tubing over brush leads and solder brush leads to receptacle pins; follow pin
identification as shown on Figure 14-9.

Assemble brushes and springs to brush guide block.

Align marks and reinstall brush retainer as described in Paragraph 14-13.

Check freedom of movement of each brush by pressing it into the brush guide block and allowing
the spring to force it back out slowly.

CAUTION: DO NOT ALLOW BRUSH TO SNAP BACK.

Check resistance from each brush face to the respective receptacle pin with low range ohmmeter.
Resistance must not exceed 0.013 ohms. Probe contacting brush should have an area of .062 square
inch to provide an accurate measurement.

Check insulation resistance between brushes and from brushes to receptacle housing with 500
VDC, 1000 megohm range “Megger” (“Meg” Type Insulation Tester, James G. Biddle Company,
Plymouth Meeting, Penna., or equivalent). Resistance should not be less than 10 megohms for one
minute.

Install assembly on aircraft and check alignment. Safety all bolts.

14-15. ALIGNMENT OF NEW BRUSHES.

Any time the brush block assembly is dismounted, the alignment at reinstallation must be checked as
described in Paragraph 14-11 and Figure 14-7.

NOTE: A brush alignment template may be fabricated per Figure 14-10e.

14-16. SLIP RINGS.

14-17. ALIGNMENT OF SLIP RING ASSEMBLY.

Excessive slip ring run-out will result in severe arcing between the slip ring and brushes and cause rapid
brush wear. If the run-out is not corrected, rapid deterioration of the slip ring and brush contact surfaces
will result and lead to eventual failure of the Deicing System. Check the slip ring run-out with a dial
indicator securely attached to the engine with the pointer resting on the slip ring. (Refer to Figure 14-6.)
Rotate the propeller slowly noting the run-out indicated on the gauge. The total run-out must not exceed
0.005 inch ± 0.0025 inch and 0.002 inch in any 4 inch interval of slip ring travel.

NOTE: Some error may be induced in the readings by pushing in or pulling out on the propeller. Care

must be taken to exert a uniform push or pull.

Small amounts of run-out may be corrected by varying the torque on the slip ring mounting bolts (AN-
47A) between 40 to 100 inch-pounds to obtain the required flatness.

14-18. REPLACEMENT OF SLIP RING ASSEMBLIES.

Slip ring assemblies that are open or shorted electrically, cracked or damaged structurally, or which have
damaged surfaces beyond the scope of minor repair to clean up, should be replaced.

Piper PA-34-200T Seneca II, Service Manual

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