TM 11-5820-890-30-4
CHAPTER 16
LOUDSPEAKER-CONTROL UNIT, LS-671/VRC
MAINTENANCE INSTRUCTIONS
Subject
Section
Page
Principles of Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
16-1
Repair Parts, Special Tools, TMDE, and Support Equipmemt . . . . . . . . . . . . . . . . . . . . . . . II
16-3
Troubleshooting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ill
16-3
Maintenance Procedures
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IV
16-24
Preparation for Storage or Shipment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
V
16-31
Section I. Principles OF OPERATION
Subject
Para
Page
Introduction
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-1
16-1
Rear Cover Assembly (15A1)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-2
16-1
Speaker Case/Flexible Cable Assembly (16A2 and 15A3) . . . . . . . . . . . . . . . . . . . . . . . . . 16-3
16-2
Loudspeaker
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16-4
16-2
16-1. INTRODUCTION.
The Loudspeaker-Control Unit, LS-671/VRC (loudspeaker) is used in conjunction with vehicular mounted radio
systems. Its basic function is to permit remote transmit and receive operation of the RT thru the loudspeaker.
Other functions included are remote power ON/OFF control of the mounting adapter or power supply adapter,
volume control of the loudspeaker, and a provision for connecting a handset.
The loudspeaker-control unit, LS-671/VRC has three main sections which are:
a.
Rear Cover Assembly (15A1)
b. Speaker Case/Flexible Cable Assembly (15A2 and 15A3)
c.
Loudspeaker
They are described in the following paragraphs:
16-2. REAR COVER ASSEMBLY (15A1).
The rear cover assembly is mounted on the rear of the LS-671/VRC. It provides three basic functions:
a.
It provides an environmental seal for the LS-671/VRC.
b. It contains the LS-671/VRC CCA (15A1A1) that controls the operation of the LS-671/VRC.
c.
It contains the amplifier module assembly (15A1A2) that comprises a voltage regulator, loudspeaker
amplifier, handset amplifier, and buffering amplifier.
The input power must be 22 to 32 V dc. The current required depends on the output loads. Normally, 150 to
500 mA of input current is required. A schematic diagram of the LS-671/VRC is included in figure FO-30.
16-1
