Midland 79-892 CB Radio Schematic Diagram

Circuit Overview

This document presents a detailed schematic diagram for the Midland 79-892 CB radio. The diagram illustrates the complex electronic circuitry, including various stages such as oscillators, amplifiers, mixers, detectors, and control circuits. Key components like transistors (e.g., 2SC710, 2SC460), integrated circuits (e.g., TA7310P), resistors, capacitors, inductors, and switches are depicted with their respective values and part numbers.

The schematic is organized into functional blocks, each representing a specific part of the radio's operation. These blocks include:

• VCO (Voltage Controlled Oscillator) Block
• Oscillators (OSC 1, OSC 2, OSC 3)
• PLL (Phase Locked Loop)
• Buffer stages
• RF Amplifier (RF AMP)
• DC Switches
• Mixer stages
• Noise Blanker
• AM IF Amplifier (AM IF AMP)
• SSB IF Amplifier (SSB IF AMP)
• SSB Detector (SSB DET)
• AF ALC (Automatic Level Control)
• AF Amplifier (AF AMP)
• Squelch circuit
• Automatic Voltage Regulator (AVR)

Connections between these stages are clearly indicated by lines, with specific component references (e.g., R1, C1, Q1) and voltage levels noted where applicable. The diagram also shows the front panel controls and the microphone unit connections.

Component Identification and Functionality

The schematic provides a comprehensive list of components used in the Midland 79-892 CB radio. Each component is labeled with its type and value. For transistors, the part numbers (e.g., 2SC710, 2SC460) and their pin configurations are implicitly shown by their connection to other components. Integrated circuits like the TA7310P and TA7205P are also detailed.

The diagram serves as a technical blueprint for understanding the radio's internal workings, aiding in troubleshooting, repair, and modification. It details the signal path from the antenna input through various amplification and processing stages to the audio output.

Front Panel and Microphone Unit

The schematic includes a section detailing the front panel connections and controls. This includes the microphone input jack (MIC UNIT), gain control (GAIN), volume control (VOL), squelch control (SQL), tone control (TONE), and power switch (POWER). The RF/SIG meter indicator is also shown.

The microphone unit is depicted with its pinout, indicating connections for transmit (TR) and receive (R) signals, as well as ground.