Motorola Xtl5000 Detailled 6881096c74 B Manual
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6881096C74-BMay 25, 2005 Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting 4-7 4.6.3 Out-of-Lock Condition The probable cause of an out-of-lock condition is a failure in the synthesizer circuit. If the voltages on the AUX 1*, AUX 2*, AUX3*, and AUX4* lines do not conform to required output frequency in Table 4-5, troubleshoot the synthesizer. If the AUX 1* to AUX 4* voltages are correct but the synthesizer feedback level is not within the range indicated, troubleshoot the...
Page 152
May 25, 20056881096C74-B 4-8Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting Figure 4-1. Frequency Generator Unit DC Power Supply Distribution (VHF) MAEPF-27803-O_VHF 13.8 VDC from Battery or Power Supply Q0503 Switched A+ Switched A+ (SW_A+) 9.3V Regulated 5.0V Regulated8.2V RegulatedK9.1 3.0V Regulated U0950 9.3V Regulator U0505 5.0V Regulator U3750 3.0V Regulator Y3750 16.8 MHz Reference Oscillator and U3752 BufferQ3756 8.2V Superfilter Q3753,Q3754 TX VCOs and...
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6881096C74-BMay 25, 2005 Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting 4-9 Figure 4-2. Frequency Generation Unit Block Diagram (VHF) Table 4-6. LV Frac-N U3751 Pin Descriptions (VHF) Pin No.Pin NameDescription 1AUX2 Auxiliary logic output, high selects Low TX VCO 2AUX3 Auxiliary logic output, high selects Low RX VCO 3AUX4 Auxiliary logic output, high selects High RX VCO 4LOCK Lock detect—logic high indicates in-lock condition 5PD_VDD 3.0-V supply (phase detector) 6GROUND...
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May 25, 20056881096C74-B 4-10Troubleshooting Procedures: VHF (136–174 MHz) Band Main Board Troubleshooting 13 VRO 3.0-V supply for reference oscillator warp circuitry 14VMULT2 Not used 15VMULT1 Not used 16INDMULT Not used 17— No connection 18REFSEL Not used 19FREFOUT Not used 20AVDD 3.0-V supply (analog) 21VBPASS Not used 22GND Ground (analog) 23XTAL1 16.8 MHz reference oscillator input 24XTAL2 Not used 25WARP Reference oscillator warp output 26SFCAP Superfilter bypass node 27SFBASE Superfilter control...
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6881096C74-BMay 25, 2005 Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-11 Figure 4-3. Waveform Representation During Programming of the LV Frac-N IC (U3751) NOTE:The above waveforms are representations only. 4.6.5 No or Low Output Power (TX or RX Injection) In addition to the schematic and theory of operation, refer to the transmitter injection troubleshooting flowchart and the receiver injection trouble shooting flowchart in Chapter 5. The charts will guide...
Page 156
May 25, 20056881096C74-B 4-12Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting NOTE:The UHF band radios use high-side injection with an IF frequency of 109.65 MHz; therefore, the receive VCO frequencies are 109.65 MHz higher than the selected radio channel frequencies. NOTE:If a failure is indicated in any of the VCOs, whose operation is defined in the table above, then the respective circuit should be checked to ensure proper bias is being applied to the...
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6881096C74-BMay 25, 2005 Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-13 4.7.2 FGU Troubleshooting Aids The following illustrations are additional service aids for troubleshooting the frequency generation unit. •Figure 4-4 is a block diagram of the DC distribution for the frequency generation unit. •Figure 4-5 on page 4-14 is a block diagram of the frequency generation unit. •Table 4-9 on page 4-14 describes the function of pins on the LV Frac-N IC U5752....
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May 25, 20056881096C74-B 4-14Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting Figure 4-5. Frequency Generation Unit Block Diagram (UHF Range 1) Table 4-9. LV Frac-N U6751 Pin Descriptions (UHF Range 1) Pin No.Pin NameDescription 1AUX2 Auxiliary logic output 2AUX3 Auxiliary logic output 3AUX4 Auxiliary logic output 4LOCK Lock detect—logic high indicates in-lock condition 5PD_VDD 3.0-V supply (phase detector) 6GROUND Ground (digital) 7DATA SPI data I/O 8CLK SPI clock...
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6881096C74-BMay 25, 2005 Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting 4-15 15 VMULT1 Not used 16INDMULT Not used 17— No connection 18REFSEL Not used 19FREFOUT Not used 20AVDD 3.0-V supply (analog) 21VBPASS Not used 22GND Ground (analog) 23XTAL1 16.8 MHz reference oscillator input 24XTAL2 Not used 25WARP Reference oscillator warp output 26SFCAP Superfilter bypass node 27SFBASE Superfilter control node for Q5752 28SFOUT Superfilter output 29— No connection 30SFIN...
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May 25, 20056881096C74-B 4-16Troubleshooting Procedures: UHF Range 1 (380–470 MHz) Band Main Board Troubleshooting Figure 4-6. Waveform Representation During Programming of the LV Frac-N IC (U5752) NOTE:The above waveforms are representations only. 4.7.3 Out-of-Lock Condition The probable cause of an out-of-lock condition is a failure in the synthesizer circuit. If the voltages on the AUX lines do not conform to Table 4-8 on page 4-12, troubleshoot the synthesizer. If the AUX pins are correct, but the...