TM-9-2320-273-34
TRUCK TRACTOR, LINE HAUL; LIGHT EQUIPMENT TRANSPORTER; TRUCK CHASSIS; MEDIUM EQUIPMENT TRANSPORTER
TECHNICAL MANUAL; DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE
DECEMBER 1980
TM-9-2320-273-34 - Page 129 of 801
TM 9-2320-273-34
CHAPTER 5
REPAIR OF ELECTRICAL SYSTEM
Section 1. ALTERNATOR AND TRANSFORMER-RECTIFIER
5-1. Description.
a. Alternator.
The alternator is a self-load limiting device featuring a fully adjustable, built-in,
solid-state voltage regulator. The rated output of the alternator is 85 amperes at 14 volts dc and has
a maximum speed of 8000 rpm. Six silicon diodes mounted in heatsinks convert alternating current
into direct current. A capacitor connected between the heatsinks assists in suppressing transient volt-
age spikes which could possibly injure the diodes. The brushes and voltage regulator are located in a
waterproof housing and may be removed for replacement or inspection without dismantling the
entire alternator. The regulator is also equipped with transient voltage protection and will withstand
instantaneous opening of the charging circuit under full load conditions.
b. Transformer-Rectifier.
The transformer-rectifier consists of a 3-phase transformer to obtain
electrical isolation from the alternator, and a 3-phase, full wave rectifier to provide dc output. It is
energized from the ac terminals of the alternator to which it is connected by 3 leads. The transformer-
rectifier replaces the conventional series parallel switch and is used to provide a source of power for
charging the cranking batteries on 12-volt vehicles equipped with 24-volt cranking motors, The system
vehicle 12-volt batteries are charged by the alternator in the conventional manner, with the cranking
batteries being charged by the transformer-rectifier unit.
c.
Resistor Assemb/y.
The resistor assembly is a protective device which limits the current flow
from the transformer-rectifier. In the event cranking batteries become fully discharged or shorted
out, the current flow from the transformer-rectifier could become so high that it would cause a
failure to the transformer-rectifier. The resistor assembly limits the current flow to about 25 amperes
under all battery conditions.
5-2. On-Vehicle Testing.
a. Scope.
On-vehicle testing is limited to an attempt to adjust the regulator. On-vehicle trouble-
shooting is provided in chapter 2 of this manual.
5-1
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