Motorola GM300

March, 1997 68 No. 4-1
Section 4
Non-Field Servicable Components
Overview
This section explains the operation of the reference oscillator and lists all non-Þeld serviceable components in the
GM300 moible radios.
Operation of the Reference Oscillator
The frequency stability of the reference oscillator in the GM300 mobile radios is maintained by electronically mea-
suring the temperature of the oscillatorÕs crystal, computing the control voltage needed to accurately compensate
for the temperature-dependent frequency shift of the crystal, and applying this voltage to the tuning varactors in
the oscillator circuit.
For accurate temperature compensation, the characteristics of the oscillator and crystal are measured at the factory,
and this information is programmed into the microcomputer on the logic board.
Non-Field Servicable Components
Field-replacement of the microcomputer on the logic board, or of any components in the reference oscillator or tem-
perature-sensing circuit on the RF board, will impair the accuracy of this compensation technique. For this reason,
these components cannot be replaced in the Þeld . If any of these components require service, the entire RF or logic
board must be replaced. The Radio Service Software calibration procedure for board replacement must be per-
formed after the new board has been installed. This step re-enters the temperature characteristic of the new oscilla-
tor into the old microcomputer, or vice-versa.
The following components are not Þeld-serviceable:
Ref. No. Part No. Description Location
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C151 21-13740B73 chip capacitor, 1000 pF RF Board
C152 21-13740B47 chip capacitor, 82 pF RF Board
C153 21-13740B25 chip capacitor, 10 pF RF Board
C154 21-13741B45 chip capacitor, .01 uF RF Board
C155, 156 21-13740B55 chip capacitor, 180 pF RF Board
C157 21-13741B45 chip capacitor, .01 uF RF Board
C158 08-11051A15 poly capacitor, 0.22 uF, 63 V RF Board
C159 21-13740B35 chip capacitor, 27 pF RF Board
C160 21-13740B29 chip capacitor, 15 pF RF Board
C161 21-13740B73 chip capacitor, 1000 pF RF Board
C163 08-11051A17 poly capacitor, 0.47 uF, 63 V RF Board
C164 21-13741B69 chip capacitor, 0.1 uF RF Board
C165 21-13740B73 chip capacitor, 1000 pF RF Board
C166 thru 168 21-13740B49 chip capacitor, 100 pF RF Board
C176 21-13740B73 chip capacitor, 1000 pF RF Board
C177 21-13741B69 chip capacitor, 0.1 uF RF Board
CR151, 152 48-80006E10 silicon varactor SOT RF Board
CR153 48-84336R03 dual silicon SOT MMBD7000 RF Board
L151 24-80299D01 coil, tunable 17-3/4 turns RF Board
L152 24-11087A35 chip coil, 5.6 uH, 10% RF Board
Q151 48-11043C19 NPN; type M43C19/M9658 RF Board
Q152 48-11043C06 PNP; type M43C06/M9643 RF Board
R151 06-11077B15 chip resistor, 47k RF Board
R152 06-11077B11 chip resistor, 33k RF Board
R153 06-11077B15 chip resistor, 47k RF Board
R154 06-11077A34 chip resistor, 22 RF Board
R155 06-11077A98 chip resistor, 10k RF Board
R156 06-11077B03 chip resistor, 15k RF Board
R157 06-11077A78 chip resistor, 1.5k RF Board
R158 06-11077A74 chip resistor, 1k RF Board
R161 06-11077A98 chip resistor, 10k RF Board