Motorola Cm Radio Midband 66 88mhz Information Manual
Have a look at the manual Motorola Cm Radio Midband 66 88mhz Information Manual online for free. It’s possible to download the document as PDF or print. UserManuals.tech offer 249 Motorola manuals and user’s guides for free. Share the user manual or guide on Facebook, Twitter or Google+.
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 Out-of-Lock Receiver (Sheet 1 of 2) Monitor TP200 at turn-on See figure for typical trace TP200 Is Voltage correct for freq? Typ. 4V for 66MHz to 11v for 88MHz (Rx freq.) No Check C2078, R217, R224, C2074, R200, R234 Check U200-4 (lock detect line) Check U200-45, 43 lines. If all ok, replace U200 Ye s TP200 Is ramp-up slope correct? Typ.14V in 500msNo Ye s START Ye sNo Go to ‘A’ sheet 2 of 2 Go to Rx VCO Section Ye s No TP200 Does voltage reach typ. 14.7V Check LO level TP1 approx -18dBm into 50 OhmsCheck voltage on U200-47 typ. 14.7V No No Ye s Is freq approx 118MHz TP200 approx 14.7V ? or
Troubleshooting Flow Chart for Out-of-Lock Receiver (Sheet 1 of 2) 3-3 1.1Troubleshooting Flow Chart for Out-of-Lock Receiver (Sheet 2 of 2) Ye s Ye s No From ‘A’ sheet 1 of 2 TP200 Does Voltage stay
3-4TROUBLESHOOTING CHARTS 2.0 Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 4) START No Check components between Q100 and RF output, Antenna Switch D104, D103, VR102 and Q106, Q103 and associated bias circuitry. Check DC volts present at anode of D103. No or too low power when keyed Current increase when keyed? Check power settings, tuning, R142, R143, R156 & components between U103 Pin 3 and ASFIC Pin 6 before replacing ASFIC Control Voltage at TP150 >1.6V? Check Harmonic Filter components C1537 to Antenna Connector >1A Voltage U103 pin 5 = 4.7V? U103 Pin 3 2Vdc Check 9.3V Regulator U501, R180 & R181 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 >800mA &
Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 4) 3-5 2.1Troubleshooting Flow Chart for 25W Transmitter (Sheet 2 of 4) Check PA Stages Quick check of PA devices. Connect power supply. Key radio. Replace Q100. Re-tune PA Bias with Tuner. Check 13.8v present at drain Q100. Disconnect power supply, measure R131 to Ground. 10kOhm? Ye s No Measure R147 to Ground. Replace Q105. 22kOhm? Ye s No Go to ‘A’ sheet 3 of 4
3-6TROUBLESHOOTING CHARTS 2.2Troubleshooting Flow Chart for 25W Transmitter (Sheet 3 of 4) Ye s >3V Check Q102, R139, R166, R126, R169, R138, R175, R147 DC Voltage at Q101 & Q102 base=0? DC Voltage at U103 Pin 8 Check U403 Check resistive network at Pin 9 and 10 of U103 before replacing U101 Measure DC Voltage at U102 Pin 1 Pin 1 Voltage Check resistive network at Pin 2 & 3 of U102 before replacing Q105 Check Final PA Stages DC Voltage at U103 Pin 3 = 8.8V Check U102 before replacing Q105 DC Voltage at U103 Pin 10=8.8V Check Q101, Q102, R153, R136, R165, R122, R168 & R137 Check U103 before re- placing U101 No No Ye s >5.0V 2.0 to 5.0V 2-3V Ye s No
Troubleshooting Flow Chart for 25W Transmitter (Sheet 1 of 4) 3-7 2.3Troubleshooting Flow Chart for 25W Transmitter (Sheet 4 of 4) No Ye s Ye sNo Check Final PA Stage PA_Bias Voltage at R134 RF Voltage after C1044 >100mV? Voltage across R122 >50mV? RF Voltage Q105 gate >250mV? RF Voltage Q100 gate >1.0V? Check components between Q100 & antenna connector Replace Q100 Check FGU Check components between C1044 & C182 Check components between C182 & Q105 Check components between Q105 & Q100 No No Ye s Ye s 2-3VSupply Voltage Check voltage varies as bias softpot is tuned (in small steps) via the Global Tuner. Check Bias Tuning, R134, R131, R105 & R106 before replacing ASFIC U504. >100mV &
3-8TROUBLESHOOTING CHARTS 3.0 Troubleshooting Flow Chart for Synthesizer (Reference Oscillator) Incorrect or no µP clock signal TP403 NOYES NO YES Power-up default freq. Fault with ASFIC or Controller section Check U504-28 should be 16.8MHz YES NOCheck Y201 and associated circuitry Check U504 and C504, C5025, R5033 Reference Oscillator working Freq. = 14.7MHz or 7.4MHz ? TP403 Freq. = 3.68MHz 0.5Vpp Check U504-28 Check Y202-1 should be 16.8MHz 0.5VppNO YES Faulty U200, or R229
Troubleshooting Flow Chart for VCO3-9 4.0 Troubleshooting Flow Chart for VCO No Receive VCO Signal at TP1 >7V at Q2751D ?NO YES NO YESCheck Q2742, R2743 U200-2 should be 0V Check Rx - Tx switching Q2742, Q2752 (should be turned on) Check Q2741 and associated circuitry. Use Hi - impedance probe to check frequency YES NO Check Rx VCO parts
3-10TROUBLESHOOTING CHARTS 5.0 Troubleshooting Flow Chart for Receiver (Sheet 1 of 2) Bad SINAD Bad 20dB Quieting No Recovered AudioSTART Audio at pin 8 of U2 ?Check Controller (in the case of no audio) OR ELSE go to “B” Ye s No Spray or inject 21.4MHz into XTAL Filter FL3101 Audio heard ?BYe s No Check 2nd LO (20.945MHz) at C53 LO present ?BYe s Check voltages on U2Biasing OK ? No No A Ye s Check Q6 bias for faults Replace Q6 Go to B Ye s No Check circuitry around U2. Replace U2 if defectCheck circuitry around Y2 Replace Y2 if defectVoltages OK? Ensure that all Power Supplies are correct, as detailed in paragraph 6.