Gravely Convertible 10 Shop Manual page 22

MAGNETO-ALTERNATOR SYSTEMS (C-10A and C-12)
The 10 Amp Magneto-Alternator System consists of a magneto ignition circuit and a battery charging or
alternator circuit. This system should not be confused with other magneto-alternator systems which provide
energy for ignition and lighting but do not have battery charging capabilities.
The alternator system consists of three major components: a permanent magnet ring bolted to the inside
rim of the flywheel, an alternator stator assembly which is affixed to the engine bearing plate and a rectifier-
regulator unit which is externally mounted on the tractor. Identification of engines with this system can be
made through the rectifier-regulator unit as shown on the accompanying illustration.
Operation: As the magnet ring is rotated around the stator, an Alternating Current is generated in the stator
winding. The AC thus produced is rectified to Direct Current in the rectifier-regulator unit. This is
accomplished through the use of solid state (no moving parts) electronic devices which are arranged to form a
full wave bridge rectifier. Regulation is also provided by electronic devices which "sense" the counter-voltage
created by the battery to control or limit the charging rate. Since heat is generated in operation of certain of
these electronic devices, cooling fins are provided on the rectifier-regulator to help dissipate the heat. The unit
should be mounted with the fins in a vertical position and preferably in a well ventilated area.
Service: The same service procedure used for the conventional magneto-ignition system also applies to this
magneto circuit. The magneto coil is secured to a stator post by a tab which is wedged between the post and
the inside of the coil. If coil replacement becomes necessary, the flywheel must first be removed to gain
access to the stator. The retaining tab must be pulled out of the slot before the faulty coil can be removed
from the stator post. When installing new coil, position tab with clip in hole on stator, then slip coil over tab
and stator post. After the coil is in place, bend protruding end of tab over to prevent interference with magnet
ring.
No adjustments are possible on the alternator system and field service on this system is not recommended.
The faulty part should be replaced by a new part. Repair of the rectifier-regulator, which is a sealed unit,
requires the use of special test equipment available only at the place of manufacture. Stator repairs must also
be performed with special equipment. The accompanying Trouble Analysis Chart can be used to pinpoint the
faulty part.
Precautions
1. Battery polarity must be correct. Negative ground systems are used.
2. Prevent alternator leads (AC) from touching or shorting. This could permanently damage the stator.
3. Disconnect leads at rectifier-regulator before electric welding is done on equipment in common
ground with engine.
Figure 17 Rectifier - Regulator Assembly Figure 18 Alternator Stator Assembly
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