Motorola Mtx Series Detailed Rev 6881088c46 E Manual

							MANUAL REVISION
12-26-03
®
© Motorola, Inc. 2003
8000 West Sunrise Boulevard
Fort Lauderdale, Florida 33322
*FMR2045A-2*
FMR-2045A-2
HT Series, MTX Series, PRO Series
Professional Series
Two-Way Portable Radios
Detailed Service Manual
6881088C46-E
REVISION CHANGE:
This manual revision contains theories of operation, schematics, board layouts, and troubleshooting 
flowcharts for Professional Series radios with the following boards installed:
Use the information provided in this manual revision to supplement your Professional Series Two-Way 
Portable Radios Detailed Service Manual, Motorola publication part number 6881088C46-E.
NOTE:Radio model charts and specifications information can be found in the appropriate Basic Service 
Manual for the radio model you are servicing.
UHF (403 - 470 MHz) Main Board PCB No. 8486458Z02*
UHF Band 2 (450 - 527 MHz) Main Board PCB No. 8486686Z01*
VHF (136 - 174 MHz) Main Board PCB No. 8486473Z03*
* Indicates parts that cannot be ordered.
Publication Title Part number
HT1250
LS Professional Series Two-Way Radio 
Basic Service Manual6864110R15 
						

							December 26, 2003 2 FMR-2045A-2
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							Table of Contents
REVISION CHANGE: ................................................................................................................................. 1
Chapter 1 UHF Theory of Operation ............................................................................... 7
1.1 Transmitter........................................................................................................................................ 7
1.1.1 General ................................................................................................................................ 7
1.1.2 Power Amplifier.................................................................................................................... 7
1.1.3 Antenna Switch .................................................................................................................... 8
1.1.4 Harmonic Filter .................................................................................................................... 8
1.1.5 Antenna Matching Network..................................................................................................8
1.1.6 Power Control Integrated Circuit (PCIC) .............................................................................. 8
1.2 Receiver............................................................................................................................................ 9
1.2.1 Receiver Front-End.............................................................................................................. 9
1.2.2 Receiver Back-End ............................................................................................................ 10
1.3 Frequency Generation Circuitry ...................................................................................................... 10
1.4 Synthesizer ..................................................................................................................................... 11
1.5 Voltage-Controlled Oscillator (VCO) ............................................................................................... 12
Chapter 2 UHF Circuit Board Layouts, Schematic Diagrams and Parts List............ 15
2.1 Notes for All Schematics and Circuit Boards ..................................................................................15
2.2 Circuit Board/Schematic Diagrams and Parts List .......................................................................... 17
Chapter 3 UHF Troubleshooting Charts....................................................................... 31
3.1 Troubleshooting Flow Chart for Controller ...................................................................................... 31
3.2 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2) ................................................................ 32
3.3 Troubleshooting Flow Chart for Receiver (Sheet 2 of 2) ................................................................ 33
3.4 Troubleshooting Flow Chart for Transmitter ...................................................................................34
3.5 Troubleshooting Flow Chart for Synthesizer...................................................................................35
3.6 Troubleshooting Flow Chart for VCO.............................................................................................. 36
Chapter 4 UHF Band 2 Theory of Operation ................................................................ 37
4.1 Transmitter...................................................................................................................................... 37
4.1.1 General .............................................................................................................................. 37
4.1.2 Power Amplifier.................................................................................................................. 37
4.1.3 Antenna Switch .................................................................................................................. 38
4.1.4 Harmonic Filter .................................................................................................................. 38
4.1.5 Antenna Matching Network................................................................................................ 38
4.1.6 Power Control Integrated Circuit (PCIC) ............................................................................ 38
4.2 Receiver.......................................................................................................................................... 39
4.2.1 Receiver Front-End............................................................................................................ 39
4.2.2 Receiver Back-End ............................................................................................................ 40
4.3 Frequency Generation Circuitry ...................................................................................................... 40
4.4 Synthesizer ..................................................................................................................................... 41
4.5 Voltage-Controlled Oscillator (VCO) ............................................................................................... 42
Chapter 5 UHF Band 2 CB Layouts, Schematic Diagrams, and Parts List ............... 45 
						

							4Table of Contents
December 26, 2003FMR-2045A-2
5.1 Notes For All Schematics and Circuit Boards .................................................................................45
5.2 Circuit Board/Schematic Diagrams and Parts List .......................................................................... 47
Chapter 6 UHF Band 2 Troubleshooting Charts .......................................................... 61
6.1 Troubleshooting Flow Chart for Controller ...................................................................................... 61
6.2 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)................................................................. 62
6.3 Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)................................................................. 63
6.4 Troubleshooting Flow Chart for Transmitter ...................................................................................64
6.5 Troubleshooting Flow Chart for Synthesizer ...................................................................................65
6.6 Troubleshooting Flow Chart for VCO .............................................................................................. 66
Chapter 7 VHF Theory of Operation .............................................................................. 67
7.1 Transmitter ...................................................................................................................................... 67
7.1.1 General .............................................................................................................................. 67
7.1.2 Power Amplifier .................................................................................................................. 67
7.1.3 Antenna Switch .................................................................................................................. 68
7.1.4 Harmonic Filter................................................................................................................... 68
7.1.5 Antenna Matching Network ................................................................................................ 68
7.1.6 Power Control Integrated Circuit (PCIC) ............................................................................ 68
7.2 Receiver .......................................................................................................................................... 69
7.2.1 Receiver Front-End ............................................................................................................ 69
7.2.2 Receiver Back-End ............................................................................................................ 70
7.2.3 Automatic Gain Control Circuit........................................................................................... 70
7.3 Frequency Generation Circuitry ...................................................................................................... 71
7.4 Synthesizer ..................................................................................................................................... 72
7.5 Voltage-Controlled Oscillator (VCO) ............................................................................................... 73
Chapter 8 VHF Circuit Board Layouts, Schematic Diagrams and Parts List ............ 75
8.1 Notes For All Schematics and Circuit Boards .................................................................................75
8.2 Circuit Board/Schematic Diagrams and Parts List .......................................................................... 77
Chapter 9 VHF Troubleshooting Charts ....................................................................... 91
9.1 Troubleshooting Flow Chart for Controller ...................................................................................... 91
9.2 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2)................................................................. 92
9.3 Troubleshooting Flow Chart for Transmitter ...................................................................................94
9.4 Troubleshooting Flow Chart for Synthesizer ...................................................................................95
9.5 Troubleshooting Flow Chart for VCO .............................................................................................. 96 
						

							Table of Contents5
FMR-2045A-212/26/03
List of Figures
Transmitter Block Diagram .................................................................................................................. 7
UHF Receiver Block Diagram .............................................................................................................. 9
Frequency Generation Unit Block Diagram ....................................................................................... 10
Synthesizer Block Diagram ................................................................................................................ 11
VCO Block Diagram ........................................................................................................................... 12
UHF (403-470MHz) Main Board Top Side PCB No. 8486458Z02 ..................................................... 17
UHF (403-470MHz) Main Board Bottom Side PCB No. 8486458Z02 ............................................... 18
UHF Controls And Switches Schematic Diagram .............................................................................. 19
UHF Receiver Front-End Schematic Diagram ................................................................................... 20
UHF Receiver Back-End Schematic Diagram ................................................................................... 21
UHF Synthesizer Schematic Diagram ...............................................................................................22
UHF Voltage Controlled Oscillator Schematic Diagram ..................................................................... 23
UHF Harmonic Filter Schematic Diagram ..........................................................................................24
UHF Transmitter Schematic Diagram ................................................................................................ 25
Controller ASFIC/ON_OFF Schematic Diagram ................................................................................ 30
Transmitter Block Diagram ................................................................................................................ 37
UHF Receiver Block Diagram ............................................................................................................ 39
Frequency Generation Unit Block Diagram ....................................................................................... 40
Synthesizer Block Diagram ................................................................................................................ 41
VCO Block Diagram ........................................................................................................................... 42
UHF Band 2 (450-527 MHz) Main Board Top Side PCB No. 8486686Z01 ....................................... 47
UHF Band 2 (450-527 MHz) Main Board Bottom Side PCB No. 8486686Z01 .................................. 48
UHF Band 2 Controls and Switches Schematic Diagram .................................................................. 49
UHF Band 2 Receiver Front End Schematic Diagram ....................................................................... 50
UHF Band 2 Receiver Back End Schematic Diagram ....................................................................... 51
UHF Band 2 Synthesizer Schematic Diagram ................................................................................... 52
UHF Band 2 Voltage Controlled Oscillator Schematic Diagram ........................................................ 53
UHF Band 2 Harmonic Filter Schematic Diagram ............................................................................. 54
UHF Band 2 Transmitter Schematic Diagram .................................................................................... 55
Controller ASFIC/ON_OFF Schematic Diagram ................................................................................ 60
Transmitter Block Diagram ................................................................................................................ 67
VHF Receiver Block Diagram ............................................................................................................ 69
Frequency Generation Unit Block Diagram ....................................................................................... 71
Synthesizer Block Diagram ................................................................................................................ 72
VCO Block Diagram ........................................................................................................................... 73
VHF (136-174MHz) Main Board Top Side PCB No. 8486473Z03 ..................................................... 77
VHF (136-174MHz) Main Board Bottom Side PCB No. 8486473Z03 ................................................ 78
VHF Controls And Switches Schematic Diagram .............................................................................. 79
VHF Receiver Front-End Schematic Diagram ................................................................................... 80
VHF Receiver Back-End Schematic Diagram .................................................................................... 81
VHF Synthesizer Schematic Diagram................................................................................................ 82
VHF Voltage Controlled Oscillator Schematic Diagram ..................................................................... 83
VHF Transmitter Schematic Diagram ................................................................................................ 84
Controller ASFIC/ON_OFF Schematic Diagram ................................................................................ 90 
						

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12/26/03FMR-2045A-2
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							FMR-2045A-2December 26, 2003
UHF Theory of Operation: Transmitter7
Chapter 1 UHF Theory of Operation
1.1 Transmitter
Figure 1-1.  Transmitter Block Diagram
1.1.1 General
(Refer to Figure 1-1.)
The UHF transmitter contains five basic circuits:
 Power amplifier
 Antenna switch
 Harmonic filter
 Antenna matching network
 Power control integrated circuit (PCIC)
1.1.2 Power Amplifier
The power amplifier consists of two devices:
 9Z67 LDMOS driver IC (U101)
 PRF1507 LDMOS PA (Q110)
The 9Z67 LDMOS driver IC contains a two-stage amplification with a supply voltage of 7.3V. 
This RF power amplifier is capable of supplying an output power of 0.3W (pin 6 and 7) with an input 
signal of 2mW (3dBm) (pin16). The current drain would typically be 160mA while operating in the 
frequency range of 403-470 MHz. 
The PRF1507 LDMOS PA is capable of supplying an output power of 7W with an input signal of 
0.3W. The current drain would typically be 1300mA while operating in the frequency range of 
403-470 MHz. The power output can be varied by changing the biasing voltage.PA  -  F i n a lAntenna
PA
Driver
VcontrolVcontrol
From VCO
 Jack
Antenna Switch/
Harmonic Filter/
Matching Network PCIC
Stage 
						

							December 26, 2003FMR-2045A-2
8UHF Theory of Operation: Transmitter
1.1.3 Antenna Switch
The antenna switch circuit consists of two PIN diodes (CR101 and CR102), a pi network (C107, 
L104 and C106), and two current limiting resistors (R101, R170). In the transmit mode, B+ at PCIC 
(U102) pin 23 will go low and turn on Q111 where a B+ bias is applied to the antenna switch circuit to 
bias the diodes “on.” The shunt diode (CR102) shorts out the receiver port, and the pi network, which 
operates as a quarter wave transmission line, transforms the low impedance of the shunt diode to a 
high impedance at the input of the harmonic filter. In the receive mode, the diodes are both off, and 
hence, there exists a low attenuation path between the antenna and receiver ports.
1.1.4 Harmonic Filter
The harmonic filter consists of C104, L102, C103, L101 and C102. The design of the harmonic filter 
for UHF is that of a modified Zolotarev design. It has been optimized for efficiency of the power 
module. This type of filter has the advantage that it can give a greater attenuation in the stop-band 
for a given ripple level. The harmonic filter insertion loss is typically less than 1.2 dB.
1.1.5 Antenna Matching Network
A matching network which is made up of L116 is used to match the antennas impedance to the 
harmonic filter. This will optimize the performance of the transmitter and receiver into an antenna.
1.1.6 Power Control Integrated Circuit (PCIC)
The transmitter uses the Power Control IC (PCIC), U102 to regulate the power output of the radio. 
The current to the final stage of the power module is supplied through R101, which provides a 
voltage proportional to the current drain. This voltage is then fed back to the Automatic Level Control 
(ALC) within the PCIC to regulate the output power of the transmitter. 
The PCIC has internal digital to analog converters (DACs) which provide the reference voltage of the 
control loop. The reference voltage level is programmable through the SPI line of the PCIC.
There are resistors and integrators within the PCIC, and external capacitors (C133, C134 and C135) 
in controlling the transmitter rising and falling time. These are necessary in reducing the power 
splatter into adjacent channels.
CR105 and its associated components are part of the temperature cut-back circuitry. It senses the 
printed circuit board temperature around the transmitter circuits and output a DC voltage to the 
PCIC. If the DC voltage produced exceeds the set threshold in the PCIC, the transmitter output 
power will be reduced so as to reduce the transmitter temperature. 
						

							FMR-2045A-2December 26, 2003
UHF Theory of Operation: Receiver9
1.2 Receiver
Figure 1-2.  UHF Receiver Block Diagram
1.2.1 Receiver Front-End
(Refer to the UHF Receiver Front-End Schematic Diagram on page 20 and the UHF Transmitter 
Schematic Diagram on page 25.)
The RF signal is received by the antenna and applied to a low-pass filter. For UHF, the filter consists 
of L101, L102, C102, C103, C104. The filtered RF signal is passed through the antenna switch. The 
antenna switch circuit consists of two PIN diodes (CR101 and CR102) and a pi network (C106, L104 
and C107).The signal is then applied to a varactor tuned bandpass filter. The UHF bandpass filter 
comprises of L301, L302, C302, C303, C304, CR301 and CR302. The bandpass filter is tuned by 
applying a control voltage to the varactor diodes (CR301 and CR302) in the filter.
The bandpass filter is electronically tuned by the DACRx from IC404 which is controlled by the 
microprocessor. Depending on the carrier frequency, the DACRx will supply the tuned voltage to the 
varactor diodes in the filter. Wideband operation of the filter is achieved by shifting the bandpass filter 
across the band.
The output of the bandpass filter is coupled to the RF amplifier transistor Q301 via C307. After being 
amplified by the RF amplifier, the RF signal is further filtered by a second varactor tuned bandpass 
filter, consisting of L306, L307, C313, C317, CR304 and CR305. 
Both the pre and post-RF amplifier varactor tuned filters have similar responses. The 3 dB bandwidth 
of the filter is about 50 MHz. This enables the filters to be electronically controlled by using a single 
control voltage which is DACRx.
Crystal 
Filter Mixer Va r a c t o r  
Tuned Filter RF Amp Va r a c t o r  
Tuned Filter Pin Diode 
Antenna 
Switch
RF Jack Antenna
Control Voltage
 from ASFICFirst LO
from VCO
Second LOIF Amp
455kHz
 Filter
Switch
455kHz
 Filter
455kHz
 FilterSwitch
Demodulator
RSSI
LimiterRecovered Audio
BW SELU301 
						

							December 26, 2003FMR-2045A-2
10UHF Theory of Operation: Frequency Generation Circuitry
The output of the post-RF amplifier filter which is connected to the passive double balanced mixer 
consists of T301, T302 and CR306. Matching of the filter to the mixer is provided by C381. After 
mixing with the first LO signal from the voltage controlled oscillator (VCO) using low side injection, 
the RF signal is down-converted to the 44.85 MHz IF signal. 
The IF signal coming out of the mixer is transferred to the crystal filter (FL301) through a resistor pad 
and a diplexer (C322 and L310). Matching to the input of the crystal filter is provided by C324 and 
L311. The crystal filter provides the necessary selectivity and intermodulation protection.
1.2.2 Receiver Back-End
(Refer to UHF Receiver Back-End Schematic Diagram on page 21.)
The output of crystal filter FL301 is matched to the input of first IF amplifier transistor Q302 by L330. 
Voltage supply to the IF amplifier is taken from the receive 5 volts (R5). The IF amplifier provides a 
gain of about 16dB. The amplified first IF signal is then coupled into U301 (pin 1) via C360 and L332 
which provides the matching for the first IF amplifier and U301.
Within U301, the first IF 44.85 MHz signal mixes with the 44.395 MHz second local oscillator (2nd 
LO) to produce the second IF signal at 455 kHz. The second LO signal frequency is determined by 
crystal Y300. The second IF signal (455 kHz) is then filtered by an external ceramic filter FL302 
before being amplified by the second IF amplifier within U301. Again, the signal is filtered by a 
second external ceramic filter FL303 or FL304 depending on the selected channel spacing. FL303 is 
used for 20/25 kHz channel spacing whereas FL304, for 12.5 kHz channel spacing. The simple 
circuit consisting of U302, CR312, CR313 and resistors R345, R360, R321 and R324 divert the 
second IF signal according to the BW_SEL line. The filtered output of the second IF signal is applied 
to the limiter input pin of U301.
The IF IC (U301) contains a quadrature detector using a ceramic phase-shift element (Y301) to 
provide audio detection. Internal amplification provides an audio output level around 120mVrms 
(@60% deviation) from pin 8 of U301. This demodulated audio is fed to the ASFIC_CMP IC (U404) 
in the controller section.
The IF IC (U301) also performs several other functions. It provides a received signal-strength 
indicator (RSSI) with a dynamic range of 70 dB. The RSSI is a dc voltage monitored by the 
microprocessor, and used as a peak indicator during the bench tuning of the receiver front-end 
varactor filter.
1.3 Frequency Generation Circuitry
Figure 1-3.  Frequency Generation Unit Block Diagram
Voltage 
Multiplier
Synthesizer 
U201
Dual 
Tran-
sistor
Loop 
Filter
VCOBIC 
U241Low 
Pass 
Filter
Second 
Buffer
Attenuator
To
Mixer
To
PA  D r i v e rVCP
Vmult1Aux3
Aux4
MOD Out
Modulating
Signal Vmult2Rx VCO Circuit
Tx VCO CircuitTRB
16.8 MHz
Ref. Osc.Rx Out
Tx Out