Hytera MD78X Service Manual page 9

Contents
13.5 Block Diagram ............................................................................................................................ 402
13.6 Schematic Diagram .................................................................................................................... 405
13.7 Parts List ..................................................................................................................................... 419
13.8 Troubleshooting Flow Chart ....................................................................................................... 458
14. VHF (136-174MHz 25W) Information ............................................................................................. 464
14.1 Transmitter Circuit ...................................................................................................................... 464
14.1.1 Power Amplifier ................................................................................................................ 464
14.1.2 Pre-driver Power Amplifier ............................................................................................... 464
14.1.3 Driver Power Amplifier ...................................................................................................... 465
14.1.4 Final Power Amplifier ....................................................................................................... 465
14.1.5 Antenna Switch ................................................................................................................. 465
14.1.6 Low-pass Filter ................................................................................................................. 465
14.1.7 Directional Coupler ........................................................................................................... 465
14.1.8 Output Power Control ....................................................................................................... 466
14.1.9 Thermal and Over-voltage Protections ............................................................................ 466
14.1.10 Pressure Pad Switch ...................................................................................................... 466
14.2 Receiver Circuit .......................................................................................................................... 466
14.2.1 Receiver Front-end........................................................................................................... 467
14.2.2 Receiver Back-end ........................................................................................................... 468
14.3 Frequency Generation Unit (FGU) ............................................................................................. 468
14.3.1 PLL Synthesizer ............................................................................................................... 468
14.3.2 Reference Oscillator ......................................................................................................... 469
14.3.3 PLL IC ............................................................................................................................... 469
14.3.4 VCO .................................................................................................................................. 470
14.4 PCB View .................................................................................................................................... 471
14.5 Block Diagram ............................................................................................................................ 475
14.6 Schematic Diagram .................................................................................................................... 478
14.7 Parts List ..................................................................................................................................... 492
14.8 Troubleshooting Flow Chart ....................................................................................................... 532
15. VHF (136-174MHz 50W) Information ............................................................................................. 538
15.1 Transmitter Circuit ...................................................................................................................... 538
15.1.1 Power Amplifier ................................................................................................................ 538
15.1.2 Pre-driver Power Amplifier ............................................................................................... 538
15.1.3 Driver Power Amplifier ...................................................................................................... 538
15.1.4 Final Power Amplifier ....................................................................................................... 539
15.1.5 Antenna Switch ................................................................................................................. 539
15.1.6 Low-pass Filter ................................................................................................................. 539
15.1.7 Directional Coupler ........................................................................................................... 539
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Service Manual