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DESCRIPTION
The Service Section contains the information necessary
for aligning and troubleshooting the MDR Series mobile
radio. In addition, information is provided for disassembling
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 future reference.
For complete transmitter alignment, refer to the Alignment
Procedures.
RECEIVER ADJUSTMENT
No initial adjustments to the receiver are required. Refer
to the Receiver Alignment Procedure when service is re-
quired.
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 me-
chanical and electrical failures from interrupting system
operations, routine checks should be made of all mechanical
and electrical parts at regular intervals. Preventive mainte-
nance 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 resistance. A high
resistance may cause excessive voltage drops and alternator
noise problems.
ELECTRICAL SYSTEM
Check the voltage regulator and alternator or generator
periodically to keep the electrical system within safe and
economical operational limits. Overvoltage is indicated
when the battery loses water rapidly. Usage of 1 or 2 ounces
of water per cell per week is acceptable for batteries in
continuous operation. A weak battery will often cause exces-
sive 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 become
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 opera-
tion, after the first six months, and once a year thereafter.
DISASSEMBLY PROCEDURES
Disassembly procedures are provided to completely dis-
assemble the radio. In general, reassembly is in the reverse
order. Included are procedures to remove the top and bottom
covers, duplexer, RF board, Audio Amplifier Board, Audio
Board, Logic Board, Duplexer/Interface board, system
LBI-38953
3
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