TM 5-3895-346-14
REGULATOR
ENGINE OVERHAUL
TRANSISTORIZED REGULATOR
The transistorized regulator (Fig. 1), for use on a negative ground circuit, contains a vibrating voltage regulator
unit and a field relay unit. The regulator uses a single transistor and two diodes. The transistor works in
conjunction with the conventional voltage unit having a vibrating contact point to limit the generator voltage to a
preset value. A field discharge diode reduces arcing at the voltage regulator contacts by dissipating the energy
created in the generator field windings when the contacts separate. A suppression diode prevents damage
from transient voltages which may appear in the system.
Certain transistorized regulators are equipped with a choke coil to permit the installation of a capacitor between
the regulator and the BAT terminal on installations experiencing radio interference. The capacitor suppresses
the radio noise and the choke coil acts to prevent oxidation of the voltage regulator contacts. Regulators
incorporating the choke coil are identified by a spot of green paint on the regulator base, next to the single
mounting bolthole.
CAUTION
A capacitor must not be installed unless the transistorized regulator incorporates
the choke coil.
Operation
When the engine starting switch is closed, the field relay winding is energized and causes the contacts to close.
Current then flows from the battery through the relay contacts to the regulator F2 terminal. From this point, the
current flows through the generator field winding and then through the transistor and voltage contact points to
ground.
As the generator speed increases, the increased voltage from the generator BAT terminal is impressed through
the field relay contacts across the regulator shunt winding. The magnetism
Figure 1 . Transistorized Regulator
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