Disassembly and Reassembly

DISASSEMBLY (75A)
1. Remove the four through bolts.








2. Insert a flat screwdriver between the front bracket and stator core, and pry downward.


CAUTION:
1. Do not insert the screwdriver too deeply, as there is a danger of damaging the stator coil.
2. The rear cover may be hard to remove because a ring is used to lock the outer race of the rear bearing. To facilitate removal of rear cover, heat just the bearing box section with a 200-watt soldering iron. Do not use a heat gun, as it may damage the diode assembly.


3. Secure the rotor in a vise with the pulley side up.


CAUTION: Be careful that the vise jaws do not damage the rotor.





4. Remove the pulley nut, then remove the spring washer, then the pulley, and then the spacer.
5. Remove the front bracket and two seals.
6. Remove the rotor from the vise.
7. Remove the brush holder screws, rectifier screws, and nut from the B terminal.
8. Remove the stator assembly from the rear bracket.
9. Detach the slinger from the brush holder.




10. When the stator is to be removed, unsolder the three stator leads to the main diodes on the rectifier.


CAUTION:
1. When soldering or unsoldering, use care to make sure that heat of soldering iron is not transmitted to the diodes for a long period.
2. Use care that excessive force is not exerted on the leads of the diodes.


11. When separating the rectifier from brush holder, unsolder the two plates soldered to the rectifier

DISASSEMBLY (90A)

1. Remove the nut from the "B" terminal, and rear cover.




2. When the stator is to be removed, unsolder the four stator leads to the main diodes on the rectifier.


CAUTION:
1. When soldering or unsoldering, use care to make sure that heat of soldering iron is not transmitted to the diodes for a long period.
2. Use care that excessive force is not exerted on the leads of the diodes.


3. Remove the stator assembly from the rear bracket.
4. Remove the brush holder and the rectifier.
5. Remove the four through bolts








6. Insert a flat screwdriver between the front bracket and stator core, and pry downward.


CAUTION:
1. Do not insert the screwdriver too deeply, as there is a danger of damaging the stator coil.
2. The rear cover may be hard to remove because a ring is used to lock the outer race of the rear bearing. To facilitate removal of rear cover, heat just the bearing box section with a 200-watt soldering iron. Do not use a heat gun, as it may damage the diode assembly.


7. Secure the rotor in a vise with the pulley side up.


CAUTION: Be careful that the vise jaws do not damage the rotor.




8. Remove the pulley nut, then remove the spring washer, then the pulley, and then the spacer.
9. Remove the front bracket and seals.
10. Remove the rotor from the vise.




11. When separating the rectifier from the brush holder, unsolder the two plates soldered to the rectifier.

INSPECTION (75A)

ROTOR




1. Check the rotor coil for continuity. Check to make sure that there is continuity between the slip rings. If resistance is extremely low, it means that there is a short. If there is no continuity or it there is a short circuit, replace the rotor assembly.

Resistance value : Approx. 3.1 Ohms




2. Check the rotor coil for ground. Check to make sure that there is no continuity between slip the ring and the core. If there is continuity, replace rotor assembly.

STATOR




1. Make a continuity check on the stator coil. Check to make sure that there is continuity between the coil leads. If the is no continuity, replace stator assembly.




2. Check the coil for grounding. Check to make sure that there is no continuity between the coil and the core. If there is continuity, replace the stator assembly.

RECTIFIERS




POSITIVE RECTIFIER TEST
Check for continuity between the positive rectifier and stator coil lead connection terminal with an ohmmeter. The ohmmeter should read continuity in only one direction. If there is continuity in both directions, a diode is shorted.
Replace the rectifier assembly.




NEGATIVE RECTIFIER TEST
Check for continuity between the negative rectifier and the stator coil lead connection terminal. The ohmmeter should read continuity in only one direction. It there is continuity in both directions, a diode is shorted, and the rectifier assembly must be replaced.

DIODE TRIO TEST
Check the three diodes for continuity by connecting an ohmmeter to both ends of each diode. Each diode should have continuity in only one direction.




If continuity is present in both directions, a diode is defective and the heatsink assembly must be replaced.

INSPECTION (90A)

ROTOR




1. Check the rotor coil for continuity. Check to make sure that there is continuity between the slip rings. If resistance is extremely low, it means that there is a short. If there is no continuity or if there is a short circuit, replace the rotor assembly.

Resistance value : Approx. 2.7 Ohms




2. Check the rotor coil for ground. Check to make sure that there is no continuity between slip the ring and the core. If there is continuity, replace rotor assembly.

STATOR




1. Make a continuity check on the stator coil. Check to make sure that there is continuity between the coil leads. If there is no continuity, replace stator assembly.




2. Check the coil for grounding. Check to make sure that there is no continuity between the coil and the core. If there is continuity, replace the stator assembly.

RECTIFIERS




POSITIVE RECTIFIER TEST
Check for continuity between the positive rectifier and stator coil lead connection terminal with an ohmmeter. The ohmmeter should read continuity in only on direction. If there is continuity in both directions, a diode is shorted.
Replace the rectifier assembly.




NEGATIVE RECTIFIER TEST
Check for continuity between the negative rectifier and the stator coil lead connection terminal. The ohmmeter should read continuity in only one direction. If there is continuity in both directions, a diode is shorted, and the rectifier assembly must be replaced.




DIODE TRIO TEST
Check the three diodes for continuity by connecting and ohmmeter to both ends of each diode. Each diode should have continuity in only one direction. If continuity is present in both directions, a diode is defective and the heatsink assembly must be replaced.

BRUSH REPLACEMENT




Replace the brushes it they are worn to limit line.




1. Unsolder the pigtail and remove the old brush and spring.
2. Install the brush spring and a new brush in the brush holder.




3. Insert the brush to where there is a space 2 to 3 mm (0.079 to 0.118 in.) between the limit line and the end of the brush holder.
4. Solder the pigtail to the brush holder.

REASSEMBLY








Perform reassembly in the reverse procedure of disassembly. Pay attention to the following:
Before the rotor is attached to the rear bracket, insert a wire through the small hole in the rear bracket to lock the brush. After the rotor has been installed, the wire can be removed.