QUANTUN QP-750, Service Manual

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QP-750 Service Manual
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Chapter 6 Controller Theory of Operation………………………23
6.1 Controller…………………………………………………………………………………..23
6.2 Microprocessor Circuitry………………………………………………………………….23
6.2.1 Memory Usage…………………………………………………………………………………..24
6.2.2 Control and Indicator Interface……………………………………………....…………………24
6.2.3 Interface to RSS Programming…………………………………………………………………24
6.2.4 Storage of Customer-Specific Information…………………………………….......................24
6.2.5 Sensing of Externally-Connected Accessories……………………………...........................24
6.2.6 Microprocessor Power-Up, Power-Down and Reset Routine…………………...................25
6.2.7 CPU PINs………………………………………………………………………………………….25
6.3 Audio Circuitry………………………………………………………………………………28
6.3.1. Transmit and Receive Low-Level Audio Circuitry………………………………………………28
6.3.2 Audio Power Amplifier……………………………………………………….............................28
6.3.3 Internal Microphone Audio Voice Path…………………………………………………………29
6.3.4 PTT Circuits…………………………………………………………………..............................29
6.3.5 VOX Operation……………………………………………………………….............................29
6.3.6 Programming and Flashing through Microphone Jack……………………………………….29
Chapter 7 UHF Theory of Operation………………….………….30
7.1 Introduction………………………………………………………………………………..
30
7.2 UHF Receiver…………………………………………………………………………….
30
7.2.1 Receiver Front-End……………………………………………………………………………30
7.2.2 Receiver Back-End…………………………………………………………………………….30
7.2.3 Narrowband/Wideband Switch Circuit……………………………………………………….31
7.3 UHF Transmitter
……………………………………………………………………………………..31
7.3.1 AF and Signaling……………………………………………………………………………….32
7.3.2 RF Power Amplifier…………………………………………………………………………….32
7.3.3 Antenna Switch and Harmonic Filter………………………………....................................32
7.3.4 APC……………………………………………………………………………………………...32
7.4 PLL Frequency Synthesizer
……………………………………………....................................32
7.4.1 PLL Circuit……………………………………………………………………………………..33
7.4.2 VCO…………………………………………………………………….................................33
7.4.3 Unlock Detector……………………………………………………………………………….33
7.5 Base Band and Signaling System…
…………………………………………………………...34
7.5.1 CTC/CDC………………………………………………………………………………………34
7.5.2 DTMF / 2-Tone………………………………………………………………………………..34
7.5.3 MSK…………………………………………………………………………………………….35
7.5.4 AF………………………………………………………………………………………………35
Chapter 8 UHF Troubleshooting Tables………………………….36
8.1 Troubleshooting for CPU………………………………………………………
………….36
8.2 Troubleshooting for VCO…………………………………………………………
……….37
8.3 Troubleshooting for Receive…………………………………………………………….38
8.4 Troubleshooting for Transmission………………………………………………………39