Troubleshooting; Introduction; Troubleshooting Procedure; Check Batteries - Motorola HT 1000 series Theory/Troubleshooting Manual

I. INTRODUCTION
Servicing the HT 1000, MT 2000, MTS 2000, and
MTX series portable radios requires the localization of
the malfunctioning circuit before the defective compo-
nent can be isolated and replaced. Since localizing and
isolating a defective component constitutes the most
time consuming part of troubleshooting, a thorough
understanding of the circuits involved will aid the techni-
cian in performing efficient servicing. The technician
must know how one function affects another; must be
familiar with the overall operation of the radio and the
procedures necessary to place it back in operation in
the shortest possible time.
The radio functional block diagrams, schematic dia-
grams, and troubleshooting charts provide valuable
information for troubleshooting purposes. The functional
diagrams provide signal flow information in a simplified
format, while the schematic diagrams provide the
detailed circuitry and the biasing voltages required for
isolating malfunctioning components. By using the dia-
grams, troubleshooting charts, and deductive
processes, the suspected circuit may be readily found.
To determine if analyzation of the radio is required,
perform checks such as 20dB quieting, 12dB SINAD,
noise and PL squelch sensitivity, for the receiver; and
current drain for the transmitter. These should give the
technician a general indication of where the problem is
located.
After the general problem area of the radio has been
identified, careful use of a dc voltmeter, rf millivoltmeter,
and an oscilloscope should isolate the problem to an
individual component.
II. TROUBLESHOOTING PROCEDURE
Each time that the radio is turned on, a microcom-
puter self-test occurs. A 1600Hz alert tone is generated
for approximately 500 milliseconds to indicate that the
microcomputer is functioning properly. If the alert tone is
not heard (and the alert tones have not been disabled
via the Radio Service Software), there is a problem with
the radio.
Following the microcomputer self-test, a synthesizer
self-test occurs. A continuous 1600Hz alert tone is gen-
erated if the synthesizer test is not successful. If this
condition occurs (continuous alert tone) refer to the
VCO/synthesizer troubleshooting chart.
When a radio performs unsatisfactorily, the following
procedures should help localize the fault.
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TROUBLESHOOTING

A. Check Batteries
The first step in localizing a problem is to check the
battery voltage under load. With the transmitter turned
on (keyed), check the battery voltage. A convenient way
to do this is to remove the front cover and monitor the
B+ line with a voltmeter (with respect to ground). The
measured load voltage should not be less than seven
volts. Even though the transmitter may operate at a
lower voltage, operation would be marginal and for only
a short period of time. Low-voltage transmit operation is
indicated by the flashing LED on top of the radio. If the
measured voltage is zero volts, check the battery. The
recommended procedure is to replace, or recharge, the
battery if the voltage is below seven volts under load.
B. Alignment
Strict adherence to the published procedures is a
prerequisite to accurate alignment and proper evalua-
tion of the performance of the radio. The selection of
test equipment is critical. The use of equipment other
than that recommended should be cleared through your
Motorola Area Representative to ensure that it is of
equivalent quality.
The service technician must observe good servicing
techniques. The use of interconnecting cables that are
too long, poorly positioned (dressed), or improperly ter-
minated will result in erratic meter readings. As a result,
it will not be possible to tune the radio to the desired
specifications.
Use the recommended test equipment setup and
proper connections for alignment and adjustments.
Refer to the detailed procedures supplied in the applica-
ble service manual.
C. Check Overall Transmitter Operation
If the battery voltage is sufficient, check the overall
performance of the transmitter. A good overall check of
the transmitter is the rf power output measurement.
This check indicates the proper operation of the trans-
mitter amplifier stages. A properly tuned and operating
transmitter will produce the rated rf output into a 50-ohm
load with a dc input of 7.5 volts (refer to "Transmitter
Alignment Procedure," located in the service manual, for
specific rf output). If the power is less than rated rf out-
put, refer to the applicable transmitter troubleshooting
chart.