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Motorola Cm Radio Vhf2 Information Manual

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    							Chapter 3
    TROUBLESHOOTING CHARTS
    This section contains detailed troubleshooting flowcharts. These charts should be used as a guide in 
    determining the problem areas. They are not a substitute for knowledge of circuit operation and 
    astute troubleshooting techniques. It is advisable to refer to the related detailed circuit descriptions 
    in the theory of operation sections prior to troubleshooting a radio.
    Most troubleshooting charts end up by pointing to an IC to replace. It is not always noted, but it is 
    good practice to verify supplies and grounds to the affected IC and to trace continuity to the 
    malfunctioning signal and related circuitry before replacing any IC. For instance, if a clock signal is 
    not available at a destination, continuity from the source IC should be checked before replacing the 
    source IC. 
    						
    							3-2TROUBLESHOOTING CHARTS
    1.0 Troubleshooting Flow Chart for Receiver RF (Sheet 1 of 2)
    Problem in 12 KHz and 
    25 KHz channel spacing
    9V on
    R310 (LNA)
    OK?Check
    RX_ENNoGo to 
    DC Section
    Ye s
    RX_EN
    ON ?NoCheck Q306, Q300 
    and U403Ye s
    START
    LOC_DIST
    ON?Check Q304, D305 
    and U403
    LO
    POWER
    OK ?
    Go to SYN 
    Section
    Ye s
    Ye s No
    No
    Go
    to A
    Ye s
    3 V
    to U301
    Okay ?No
    Check
    LOC_DIST
    Go to
    DC Section
    Ye s
    Check D301-304
    Replace IF Filters( FL304, FL301)
    If problem in 25 KHz spacing
    Check
    TPI
    Check 5V
    on R336 
    5V
    (IF AMP)
    OK ?Go to 
    DC SectionYe s NoCheck 3V
    on R339  
    						
    							Troubleshooting Flow Chart for Receiver RF (Sheet 1 of 2) 3-3
    1.1Troubleshooting Flow Chart for Receiver (Sheet 2 of 2)
    3V
    (IFIC -Vcc)
    OK ?
    Installation
    OK ?
    Ye s
    Ye s No
    No
    A From
    Check visually
    all receiver
    components
    installation ?
    Inject - 40dBm (CW)
    to RF connector
    Check Power on
    C332 
    RF
    Power
    > -28 dBM?Ye s NoCheck Power on
    C336 
    Go to 
    DC Section
    Check 
    the component
    Antenna to Mixer 
    circuitry problem
    Replace 
    Q303, Q301
    Check passive
    componentsRF
    Power
    > -28 dBM?Ye s
    NoReplace 
    Q305, Q300, U302
    Check passive
    componentsCheck Y301
    44.395 MHz
    Y301
    OK?Ye s NoReplace Q302, Y300
    Check D301 - 304
    Replace Y301
    3V to
    U301
    OK?Ye s NoReplace U300Go to DC Section 
    						
    							3-4TROUBLESHOOTING CHARTS
    2.0 Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 3)
    START
    Ye s
    No
    Check components between 
    Q100 and RF output, 
    Antenna Switch D104, 
    D103, VR102 and Q106 be-
    fore replacing Q100
    No or too low power when keyed
    Current
    increase when 
    keyed?
    Check power settings, tuning 
    & components between U103 
    Pin 3 and ASFIC Pin 6 before 
    replacing ASFIC
    Control 
    Voltage at 
    TP150
    =1.5V?Check PA 
    Stages
    >1.0A
    Voltage U103 
    pin 5 = 
    4.7V?
    U103 Pin 3 
    2Vdc
    Check 9.3V 
    Regulator 
    U501
    Ye s
    Ye sNo
    No
    Ye sCheck 
    U103
    Check forward 
    Power Sense 
    Circuit
    No
    Short U100 
    Pin 3 to 
    ground
    Voltage at 
    TP150 rises?Check PA 
    Stages
    Check Forward 
    Power Sense 
    Circuit
    Ye s
    No >430mA & 
    						
    							Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 3) 3-5
    2.1Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 3)
    Ye s
    5V
    2-5V
    2-3V
    Ye s No
    3V 
    						
    							3-6TROUBLESHOOTING CHARTS
    2.2Troubleshooting Flow Chart for 25W Transmitter (Sheet 3 of 3)
    No
    Ye s
    Ye sNo
    Check Final PA Stage
    PA_Bias 
    Voltage at 
    R134 
    2.1V
    RF Voltage 
    after C1044 -
    >100mV?
    Voltage 
    across R122 
    >50mV?
    RF Voltage 
    Q105 gate 
    >100mV?
    RF Voltage 
    Q100 gate 
    >1.5V?
    Check components 
    between Q100 & 
    antenna connector
    Replace Q100
    Check FGU 
    Check components 
    between C1044 & 
    C1117
    Check components 
    between C1117 & 
    Q105
    Check components 
    between Q105 & 
    Q100
    No
    No Ye s Ye s 2-3VSupply Voltage
    Check Bias Tuning 
    R134, R131, R106 
    before replacing
    ASFIC U504
    
    						
    							Troubleshooting Flow Chart for Synthesizer3-7
    3.0 Troubleshooting Flow Chart for Synthesizer
    +5V at 
    U200 Pins
    13 & 30? 5V
     at pin 6 of 
    D200
    Is information
    from µP U403
    correct?
    Is U200 
    Pin 47
    = 13VDC?
    Is U201 Pin 19
    4.5 VDC in TX?  
    (at VCO section)
    Sta rt
    Visual 
    check of the 
    Board OK?Correct
    Problem
    Check 5V
    Regulator 
    U503
    Is 16.8MHz
    Signal at
    U200 Pin 19?
    Check
    Y201 and associated 
    parts
    Are signals
    at Pins 14 &
    15 of U200?
    Check 
    R228
    Check R201Is U200 pin 2  
    >4.5 VDC in Tx & 
    
    						
    							3-8TROUBLESHOOTING CHARTS
    4.0 Troubleshooting Flow Chart for VCO
    Are Q200
    Base at 2.4V 
    Collector at 4.5V 
    Emitter at 1.7VAre U201 Pins
    13 at 4.4V
    15 at 1.1V
    10 at 4.5V
    16 at 1.9V
    Low or no RF Signal
    at TP1
    Visual check
    of board
    OK?
    35mV DC at
    U201 Pin 19
    NO
    YES
    at base of Q200
    NO
    NO
    NO
    NO YES
    YES
    YES
    YESLow or no RF Signal
    at input to PA5V DC at U201
    Pin 14 & 18 OK?
    4.8V DC at
    U201 Pin 19
    Is RF available 
    at C2060
    YES
    YESYESYES YES NO
    NO
    NO
    NO
    NO
    Audio =180mVrms
    at “+” side of
    D205
    2.5VDC
    at D205
    If R211 is Ok,
    replace D205
    Replace R211
    Replace R212
    NONO
    YES
    YES
    TX VCO
    RX VCO
    Correct
    ProblemVisual check
    of board
    OK?
    Make sure U508 is working 
    correctly and runner 
    between U508 Pin 1 and 
    U201 Pin 14 & 18 is OK
    Check runner 
    between U200 Pin 2 
    and U201 Pin 19
    Is RF available 
    If all parts from U200 Pin 8
    to Base of Q200 are OK, 
    replace U200Check parts between 
    TP1 and Q200
    Power OK but 
    no modulation
    Check Transmiiter
    Pre Driver
    If all parts 
    associated 
    with the pins 
    are OK, 
    replace U201
    4.5V DC at
    U201 Pin 3 OK?
    YES
    NO4.5V DC at
    U201 Pin 3 OK?
    YES
    NO
    Make sure Synthesizer is 
    working correctly and runner 
    between U200 Pin 28 and 
    U201 Pin 3 is OK 3.3 DC at U201
    Pin 14 & 18 OK?
    OK?
    OK?
    If all parts associated 
    with the pins are OK 
    If L216, C2071, C2070,
    C2060 are okay
    replace U201Check 9V at R230
    YES 
    						
    							Troubleshooting Flow Chart for DC Supply (1 of 2) 3-9
    5.0 Troubleshooting Flow Chart for DC Supply (1 of 2)
    Since the failure of a critical voltage supply might cause the radio to automatically power down, 
    supply voltages should first be probed with a multimeter. If all the board voltages are absent, then 
    the voltage test point should be retested using a rising-edge-triggered oscilloscope. If the voltage is 
    still absent, then another voltage should be tested using the oscilloscope. If that voltage is present, 
    then the original voltage supply in question is defective and requires investigation of associated 
    circuitry.
    Check VDC on
    C5008
    V=3.3V
    ?Check Voltage on 
    C5043NoGo to D3_3VYe s
    9v
    						
    							3-10TROUBLESHOOTING CHARTS
    5.1 Troubleshooting Flow Chart for DC Supply (2 of 2)
    Check VDC on
    C5007
    V=3.3V
    ?Check Voltage on 
    C5041NoGo to Digital SectionYe s
    9v
    						
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