Motorola Handie-Talkie MTX Series Theory/Troubleshooting Manual page 3

TITLE
THEORY OF OPERATION (DETAILED FUNCTIONAL DESCRIPTION)
I. INTRODUCTION ...........................................................................................................................................10
II. RADIO POWER .............................................................................................................................................10
A. General....................................................................................................................................................10
B. B+ Routing and DC Voltage Distribution (for a Closed Architecture Controller
and a VHF or UHF Transceiver) .......................................................................................................10
C. B+ Routing and DC Voltage Distribution (for an Open Architecture Controller
and an 800 or 900MHz Transceiver).................................................................................................11
III. VHF/UHF TRANSCEIVER .............................................................................................................................12
A. Frequency Generation Unit (FGU) ..........................................................................................................12
B. Antenna Switch........................................................................................................................................13
C. Receiver Front End..................................................................................................................................13
D. Receiver Back End ..................................................................................................................................14
E. Transmitter ..............................................................................................................................................14
IV. 800/900MHz TRANSCEIVER BOARD ..........................................................................................................15
A. Frequency Synthesis ...............................................................................................................................15
B. Antenna Switch........................................................................................................................................16
C. Receiver Front End..................................................................................................................................16
D. Receiver Back End ..................................................................................................................................17
E. Transmitter ..............................................................................................................................................17
V. CLOSED ARCHITECTURE CONTROLLER .................................................................................................17
A. Microcomputer (U705).............................................................................................................................17
B. Controller Board Circuit Operation ..........................................................................................................19
VI. OPEN ARCHITECTURE CONTROLLER ......................................................................................................21
A. Microprocessor (U705) and Associated Circuits .....................................................................................22
B. Controller Board Circuit Operation ..........................................................................................................24
VII. UNIVERSAL CONNECTOR (See Tables 2 and 3) ........................................................................................28
I. INTRODUCTION ...........................................................................................................................................30
II. TROUBLESHOOTING PROCEDURE ...........................................................................................................30
A. Check Batteries .......................................................................................................................................30
B. Alignment.................................................................................................................................................30
C. Check Overall Transmitter Operation ......................................................................................................30
D. Check Overall Receiver Operation ..........................................................................................................31
III. VOLTAGE MEASUREMENT AND SIGNAL TRACING .................................................................................31
IV. TROUBLESHOOTING CHARTS ...................................................................................................................31
(VHF/UHF Transceiver/Closed Architecture Controller) ................................................................................32
(800/900MHz Transceiver/Open Architecture Controller) ..............................................................................33
(VHF/UHF Transmitter RF) ............................................................................................................................34
(800/900MHz Transmitter RF) .......................................................................................................................35
(VHF/UHF Receiver RF) ................................................................................................................................36
(800/900MHz Receiver RF) ...........................................................................................................................37
(VHF/UHF DC Switch) ...................................................................................................................................38
(800/900MHz DC Switch) ..............................................................................................................................39
(VHF/UHF Frequency Generation Unit - FGU) ..............................................................................................40
(800/900MHz Frequency Generation Unit - FGU) .........................................................................................41
(VHF/UHF Voltage Controlled Oscillator - VCO) ...........................................................................................42
(800/900MHz Voltage Controlled Oscillator - VCO).......................................................................................43
(VHF/UHF, Closed Architecture, No Receive Audio) .....................................................................................44
(800/900MHz, Open Architecture, No Receive Audio) ..................................................................................45
(VHF/UHF, Closed Architecture, No Transmit Deviation) ..............................................................................46
(800/900MHz, Open Architecture, No Transmit Deviation)............................................................................47
(Closed Architecture Controller).....................................................................................................................48
(Open Architecture Controller) .......................................................................................................................49
(VHF/UHF Only, VCO Crossover Frequency Tune) ......................................................................................50
ii
CONTENTS (cont.)
TROUBLESHOOTING
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