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TM 11-5820-890-30-5
CHAPTER 4
AMPLIFIER-ADAPTER, VEHICULAR AM-7239/VRC AND AM-7239B/VRC
MAINTENANCE INSTRUCTIONS
Subject
Section
Principles of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
Repair Parts, Special Tools, TMDE, and Support Equipment . . . . . . . . . . . . . . . . . . . . . . . II
Troubleshooting Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ill
Maintenance Procedures for AM-7239/VRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IV
Maintenance Procedures for AM-7239B/VRC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Preparation for Storage or Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI
Section I. PRINCIPLES OF OPERATION
Subject
Para
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
Audio Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Mounting Adapter Chassis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
Page
4-1
4-4
4-4
4-97
4-155
4-204
Page
4-1
4-1
4-2
4-2
4-1.
INTRODUCTION.
The mounting adapter’s three main sections are:
Power Supply, Amplifier-Adapter 5A1 (power supply).
Circuit Card Assembly, One-Watt Audio Amplifier 5A2 (audio amplifier).
Chassis, Electrical Equipment, Amplifier-Adapter 5A3 (mounting adapter chassis).
They are described in the following paragraphs:
4-2.
POWER SUPPLY.
The power supply is mounted on the back of the mounting adapter. It provides two basic functions:
It suppresses transients on the input power line.
It converts the dc input power into the dc voltages required by the radio components.
The input power must be 22 to 32 V dc. The current required depends on the output loads. Normally, 2 to 12 A of
input current is required. A block diagram of the power supply is included in figures FO-14 and FO-15.
a.
Transient Suppressor. The transient suppressor protects the radio from transients that may be on the
input power line. The transients, surges, and ripple on the input power line must be within the requirements of
MIL-STD-1275. The output of the transient suppressor is not short-circuit protected. If shorted to ground, CB1 will
trip. Its output is typically 0.5 V below the input voltage.
b.
DC-to-DC Converter. The output of the transient suppressor is fed into the dc-to-dc converter. It
provides the following regulated output voltage:
4-1
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