Crown Model 7TV-2 AC-DC Portable TV Schematic Diagram
This document provides the technical schematic for the Crown Model 7TV-2 AC-DC portable television. It details the electronic circuitry, including radio frequency (RF) tuning, intermediate frequency (IF) amplification, audio output, and power supply sections.
Page 1: RF, IF, and Audio/Power Supply Stages
Page 1 of the schematic covers the initial stages of signal reception and processing, along with the audio output and primary power supply components.
Antenna Input and Tuning (RF Section)
The circuit begins with antenna input options: a ROD ANTENNA and an EXT. ANT (external antenna) connection, selectable via switch Sg-1. The signal is then fed into the VHF AM-UF-28 tuner section. This section includes transistors such as Q2 (2SC683), Q3 (2SC717), Q4 (2SC682), and Q5 (2SC682), along with various resistors (R), capacitors (C), and inductors (L) that form the tuning and amplification circuits.
Intermediate Frequency (IF) Amplification
Following the tuner, the signal enters the IF amplification stages. This part of the circuit utilizes transistors like Q24 (2SA350), Q25 (2SC454), Q26 (2SC460), Q27 (2SC454), and Q28 (2SC460). Diodes CR701 and CR702 (IN60) are also present in this section, likely for detection or rectification.
Audio Output and Power Supply
The lower portion of Page 1 details the audio output amplifier and the main AC-DC power supply. Key components include transistors Q18 (2SB77A), Q19 (2SB77), and Q20 (2SB337) for audio amplification. The power supply features a main transformer (T801), rectifier diodes (CR801-4, CR901, CR001, CR002, CR003), and associated filtering and regulation components. Controls for Vertical Hold (V.HOLD), Vertical Size (V. SIZE), Vertical Linearity (V.LIN), and Vertical Bias (V. BIAS) are also indicated.
The power supply can operate from AC (220V) or DC (BATT) sources, with a VR/SW (Voltage Regulator/Switch) control (P1, AC.BATT VR/SW).
Page 2: CRT Driver, FBT, and Final Stages
Page 2 of the schematic focuses on the circuitry driving the Cathode Ray Tube (CRT), the Flyback Transformer (FBT) section, and final signal processing stages.
CRT Driver and Display Control
This section includes transistors such as Q9 (CDC-13000), Q10 (2SB75D), Q11 (2SD96), and Q12 (2SB496) which are involved in driving the CRT. It also shows components related to Picture (PIX) and Brightness controls, and connections to the CRT itself.
Flyback Transformer (FBT) and High Voltage Generation
The Flyback Transformer (FBT), labeled T1001, is a central component in this section, responsible for generating high voltages for the CRT. Associated components include diodes (CR1001-3, CR1004, CR1005), capacitors (C1001-3, C1006, C1007), resistors (R1001, R1002, R1004), and the FOCUS control, which adjusts the electron beam focus.
Horizontal Control and Audio Output
The lower part of Page 2 covers horizontal control circuits (H.HOLD, H.APP) utilizing transistors like Q14 (2SA15), Q15 (2SA15), Q16 (2SA15), and Q17 (2SC281). It also shows the final audio output stages with transistors Q21 (2SC281), Q22 (CDC9000), and Q23 (2SB468), along with associated components for sound reproduction.
