Diode replacement

(b) Press the bearing out from the

one ohmmeter lead to the end frame and one to the

diode lead. Check all three diodes in the way previously

slipring rear frame with a tube or collar that fits just inside

described.

the rear frame housing. Press the bearing out from

(b) Test lamp method. Test lamp of not

outside the housing toward the inside.

(c)

Press in the new bearing with a flat

more than 12-volts is required. Disconnect stator from

the heat sink diodes.

plate. Press in from outside of the rear frame until the

CAUTION

bearing is flush with the outside of the rear frame.

To prevent breakage of the rear frame, support it on the

Do not use 110-volt test lamp to

inside with a hollow cylinder. When installing the new

check diodes.

bearing, use extreme care to avoid misalignment or

Connect the test lamp in the same

other undue stress on the bearing. Saturate the felt seal

manner as the ohmmeter. If lamp lights in both checks

in OE 10 oil (MIL-L-21041, then reassemble felt seal

or fails to light in both checks, diode is defective. When

and steel retainer.

diode is not defective, the test lamp will light in only one

(8) Brush Replacement.

of two checks.

(a) When separating the slipring rear

2. Check all diodes and replace

frame from the rotor and front end frame assembly, the

defective ones as required.

brushes will drop down onto the shaft and come into

(4) Diode replacement.

When a diode

contact with the lubricant. If brushes are to be reused,

requires replacement. proceed as follows:

they must be thoroughly cleaned with a soft dry cloth.

CAUTION

Also.

clean the shaft thoroughly before beginning

Do not hammer diodes into position

reassembly.

as the shock will damage them.

(b) lnspect the brush springs for

(a) Support the end frame or head sink

evidence of any damage or corrosion. Be sure to

in a suitable tool and push out the old diode with an arbor

replace the brush springs if there is any doubt as to their

press or vise.

condition.

(b) Press the diode in with a suitable

tool which fits over the outer edge of the diode while

install them as follows: First, remove the two brush

supporting the heat sink or end frame.

holder screws, then remove the brush holder assembly

(5) Slipring.

from the rear frame. After installing the springs and

(a) Clean. To clean sliprings, use 400-

brushes in the brush holder, insert a piece of straight

grain or finer polishing cloth. Spin the rotor in a lathe or

wire or pin into holes at the bottom of the holder to retain

by other means and hold the polishing cloth against the

brushes. Then install the brush holder assembly onto

sliprings until they are clean.

the rear frame, noting carefully the proper alignment of

(b) Repair. Out of round or rough

parts as shown in

sliprings should be trued to 0.002-inch maximum

indicator readings in a lathe. Remove just enough

material to make the rings smooth and round. Polish

with 400grain or finer polishing cloth and blow away all

dust.

(6) Bearing (drive bearing).

(a) The drive bearing can be removed

by detaching the retainer plate screws and then pressing

the bearing from the front frame.

(b) Check the bearing; if it is in

satisfactory condition, it can be reused. It should be

cleaned in an approved cleaning solvent and lubricated

full with MILG-18709.

CAUTION

Figure 3-4. Brush holder assembly.

Do not overfill with lubricant as this could

cause the bearing to overheat.

(9) Heat sink replacement.

(a) To replace the heat sink, remove the

in with a tube or collar that just fits over the outer race. If

"BAT" and "GRO" terminals from the end frame and the

the felt seal is worn excessively or hardened, it is

screw attaching the condenser lead to heat sink.

recommended that a new retainer plate be in stalled.

(7) Bearing (Rear Frame).

(a) The slipring rear frame bearing

should be replaced if its grease supply ;is exhausted.

Never attempt to relubricate and reuse the bearing.

3-4