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THE circuits included in this Manual illustrate some of the more important applications of RCA receiving tubes; they are not necessarily examples of commercial practice. These circuits have been conservatively designed and are capable of excellent performance. The brief description provided with each circuit explains the functional relationships of the various stages and points out intended applications, major performance characteristics, and significant design features of the over-all circuit. Detailed descriptive information on individual circuit stages (for example, amplifiers, detectors, or oscillators) is given in the section on Electron-Tube Applications earlier in this Manual, as well as in many textbooks on electron tube circuits. Electrical specifications are given for circuit components to assist those interested in home construction. Lay outs and mechanical details are omitted because they vary widely with the requirements of individual set builders and with the sizes and shapes of the components employed. Circuits designed for operation from both ac and dc voltage sup plies should be installed in non-metallic cabinets or properly insulated from metallic cabinets. Potentiometer shafts and switches should make use of insulated (plastic) knobs. In practical use, no metallic part of an "ac/dc" chassis should be exposed to touch, accidental or otherwise. When such circuits are tested outside of their cabinets, a line isolation transformer such as the RCA WP-25A Iso-tap should be used. Performance of these circuits depends as much on the quality of the components selected and the care employed in layout and construction as on the circuits themselves. Good signal reproduction from receivers and amplifiers requires the use of good-quality speakers, transformers, chokes, and input sources (micro phones, phonograph pickups, etc.). Coils for the receiver circuits may be purchased at local parts dealers by specifying the characteristics required: for rf coils, the circuit position (antenna or interstage), tuning range desired, and tuning capacitances employed; for if coils or transformers, the intermediate frequency, circuit position (1st if, 2nd if, etc.), and, in some cases, the associated tube types; for oscillator coils, the receiver tuning range, the intermediate frequency, the type of converter tube, and the type of winding used (tapped or transformer coupled). The voltage ratings specified for capacitors are the minimum dc working voltages required. Paper, mica, or ceramic capacitors having higher voltage ratings than those specified may be used except insofar as the physical sizes of such capacitors may affect equipment layout. However, if electrolytic capacitors having substantially higher voltage ratings than those specified are used, they may not "form" completely at the operating voltage, with the result that the effective capacitances of such units may be below their rated value. The wattage ratings specified for resistors assume methods of construction that provide adequate ventilation; compact installations having poor ventilation may require resistors of higher wattage ratings. Circuits which work at very high frequencies or which are required to handle very wide bandwidths demand more than ordinary skill and experience in construction. Placement of component parts is quite critical and may require considerable experimentation. All rf leads to components including bypass capacitors must be kept short and must be properly dressed to minimize undesirable coupling and capacitance effects. Correct circuit alignment and oscillator tracking may require the use of a cathode-ray oscilloscope, a high-impedance vacuum-tube voltmeter, and a signal generator capable of sup plying a properly modulated signal at the appropriate frequencies. Un less the builder has had considerable experience with broad-band, high frequency circuits, he should not undertake the construction of such circuits. LIST OF CIRCUITS 29-1 AC/DC Superheterodyne Radio Receiver 29-2 AM/FM Superheterodyne Radio Receiver 29-3 FM Tuner 29-4 Three-Stage IF Amplifier/Limiter and Detector 29-5 FM Stereo Multiplex Adapter 29-6 Preamplifier for Amateur Receiver (21-, 30-, and 50-MHz Amateur Bands and 27-MHz Citizens Band) 29-7 Code-Practice Oscillator 29-8 Intercommunication Set (With Master Unit and Two or More Remote Units) 29-9 High-Fidelity Audio Amplifier (Class AB1; Power Output, 15 Watts) 29-10 High-Fidelity Audio Amplifier (Class AB1; Power Output, 30 Watts) 29-11 High-Fidelity Audio Amplifier (Class AB1; Power Output, 50 Watts) 29-12 Two-Channel Stereophonic Amplifier (Power Output, 1 Watt Each Channel) 29-13 Microphone and Phonograph Amplifier (Power Output, 8 Watts) 29-14 Two-Channel Audio Mixer 29-15 Phonograph Amplifier (Power Output, 1 Watt) 29-16 Preamplifier for Magnetic Phonograph Pickup (With RIAA Equalization) 29-17 High-Fidelity Preamplifier for Tape-Head Pickup (With NARTB Equalization) 29-18 Preamplifier for Ceramic Phonograph Pickup (Cathode-Follower Output) 29-19 Low-Distortion Preamplifier (For Low-Output, High-Impedance Microphones) 29-20 Bass and Treble Tone-Control Amplifier 29-21 Electronic Volt-Ohm Meter 29-22 Series-Type Stabilized Voltage Supply 29-23 All-Purpose Power Supplies 29-24 VHF Tuner (For Black-and-White TV Receiver) 29-25 Video IF Amplifiers and Sound-Channel Circuits (For Black-and White TV Receiver) 29-26 Video, AGC, and Sync Amplifiers, (For Black-and-White TV Receiver) 29-27 Vertical and Horizontal Deflection Circuits and High-Voltage Rectifier (For Black-and-White TV Receiver) 29-28 Low-Voltage and Heater Supply (For Black-and-White TV Receiver) 29-29 Low-Voltage Power Supply, Degaussing Circuit, and Heater Connections (For Color TV Receiver) 29-30 VHF Tuner (For Color TV Receiver) 29-31 Video- and Sound-Channel Circuits (For Color TV Receiver) 29-32 Sync, AGC, and Vertical-Deflection Circuits (For Color TV Receiver) 29-33 Horizontal-Deflection Circuit and High-Voltage Power Supply (For Color TV Receiver) 29-34 Chroma Circuits (For Color TV Receiver) 29-35 Picture Tube and Associated Circuits (For Color TV Receiver) MANUFACTURERS OF SPECIAL COMPONENTS AND MATERIALS REFERRED TO IN PARTS LIST |