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DESCRIPTION
The Service Section contains the information neces-
sary for aligning and troubleshooting the MDR Series
mobile radio. In addition, information is provided for dis-
assembling the radio and replacing chip components.
INITIAL ADJUSTMENT
After the radio has been installed as described in the
Installation Manual, the following adjustments should be
made by a certified electronics technician.
TRANSMITTER ADJUSTMENT
The transmitter has been adjusted at the factory and
should require no readjustment. However, the antenna
length should be adjusted for optimum VSWR, and the
frequency and modulation measured and recorded for fu-
ture reference. For the complete transmitter alignment,
refer to the Transmitter Alignment Procedure.
RECEIVER ADJUSTMENT
No initial adjustments to the receiver are required.
Refer to the Receiver Alignment Procedure.
RE-INSTALLATION
The radio is designed to operate in 12 volt, negative
ground vehicles only. If the mobile radio is moved to a
different vehicle, always check the battery polarity of the
new vehicle system.
PREVENTATIVE MAINTENANCE
To ensure high operating efficiency and to prevent
mechanical and electrical failures from interrupting sys-
tem operations, routine checks should be made of all me-
chanical and electrical parts at regular intervals. Preven-
tive maintenance should include the following checks.
CONNECTIONS
Ground connections to the voltage source should be
periodically checked for tightness. Loose or poor connec-
tions to the power source will cause excessive voltage
drops and faulty operation. When ground connections are
not made directly to the battery, the connection from the
battery to vehicle chassis must be checked for low imped-
ance. A high impedance may cause excessive voltage
drops and alternator noise problems.
ELECTRICAL SYSTEM
Check the voltage regulator and alternator or gener-
ator periodically to keep the electrical system within safe
and economical operating limits. Overvoltage is indicated
when the battery loses water rapidly. Use of 1 or 2 ounces
of water per cell per week is acceptable for batteries in
continuous operation. A weak battery will often cause
excessive noise or faulty operation.
MECHANICAL INSPECTION
Since mobile units are subject to constant shock and
vibration, check for loose plugs, nuts, screws and other
parts to make sure that nothing is working loose.
ANTENNA
The antenna, antenna base and all contacts may be-
come coated or poorly grounded; loss of radiation and a
weak signal will result.
ALIGNMENT
The transmitter and receiver meter readings should be
checked periodically, and the alignment "touched up"
when necessary. Refer to the Alignment Procedure in this
manual.
FREQUENCY CHECK
Check transmitter frequency and deviation. Normally,
these checks are made when the unit is first put into
operation, after the first six months, and once a year there-
after.
DISASSEMBLY PROCEDURES
Disassembly procedures are provided to completely
disassemble the radio. In general, reassembly is in the
reverse order. Included are procedures to remove the top
and bottom covers, duplexer, RF board, Audio Board,
Logic Board, Duplexer/Interface Board, System Board,
and Front Cap Assembly including the Handset/Interface
board. Refer to Figure 1, Radio Disassembly.
Remove power from the radio before servicing.
LBI-38701
NOTE
3
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