The Sony CFS-720 is a portable radio cassette-corder, designed for both US, Canadian, and E models, featuring a MEGA BASS sound system and a range of audio playback and recording capabilities.
Function Description:
The CFS-720 serves as a versatile audio device, combining an AM/FM radio tuner with a dual-cassette deck. It allows users to listen to radio broadcasts, play back pre-recorded cassette tapes, and record audio onto cassette tapes from various sources. The dual-cassette deck supports high-speed dubbing, enabling quick copying of tapes. It also features a mixing microphone input for recording external audio, and CD/LINE IN jacks for connecting external audio sources like CD players. The device is designed for both AC operation and portable use with batteries.
Important Technical Specifications:
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Audio Power Output:
- Rated 5 watts per channel minimum RMS power.
- Both channels driven from 70 – 15,000 Hz.
- Total harmonic distortion: no more than 10% in AC operation (with 6 ohms loads).
- Full-range speakers (Canadian model): 5W + 5W (at 10% harmonic distortion) in DC operation.
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Frequency Range:
- FM: 87.6 – 108 MHz
- AM: 530 – 1710 kHz
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Antennas:
- FM: Telescopic antenna
- AM: Built-in ferrite bar
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Recording System: 4-track, 2-channel stereo
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Frequency Response: 70 – 10,000 Hz
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Speakers: Full-range: 12cm (4¾ inches) dia. x 2
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Inputs:
- MIX MIC input jack (mono minijack) (1): sensitivity 3.9mV for low impedance microphone.
- CD/LINE IN jack (stereo phono) (2): input impedance 50 kilohms, sensitivity 0.43V.
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Outputs:
- Headphones jack (stereo minijack): for 16 – 68 ohm impedance headphones.
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Power Requirements:
- 120V AC, 60 Hz
- 9V DC, six size D (R20) batteries
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Power Consumption: 22W in AC operation
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Battery Life (approximate):
- FM recording with Sony New Super SUM-1 (NS) batteries: 5.5 hours.
- FM recording with Sony AM1 (N) alkaline batteries: 11 hours.
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Dimensions: Approx. 681 x 215 x 225 mm (w/h/d) (26¾ x 8½ x 8⅞ inches), not incl. projecting parts and controls.
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Weight: Approx. 6.5 kg (14 lb 5 oz) incl. batteries.
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Accessory Supplied: AC power cord (1).
Usage Features:
- Dual Cassette Deck: Features two cassette decks (Deck A and Deck B) for playback, recording, and high-speed dubbing.
- High-Speed Dubbing: Allows for quick copying of tapes from Deck A to Deck B.
- MEGA BASS: Enhances bass frequencies for a richer sound experience.
- 4-Band Graphic Equalizer: Provides adjustable sound control at 400Hz, 1kHz, 4kHz, and 10kHz, along with BALANCE controls.
- FM/AM Preset Tuning: Offers preset buttons for quick access to favorite radio stations.
- TUNING (+/-) Buttons: For manual radio tuning.
- SENS (Sensitivity) (DX/LOCAL) Button: Adjusts radio reception sensitivity.
- +10 Preset Tuning Button: For quickly navigating through groups of ten preset stations.
- FUNCTION Selector: Allows selection between TAPE/RADIO OFF (for tape playback/recording from MIX MIC), DUBBING, RADIO (for listening/recording radio), and CD/LINE IN (for listening/recording external sources).
- SPACE SOUND Button: Enhances the soundstage for a wider audio experience.
- MIX MIC Jack: Enables recording with an external microphone.
- Headphones Jack: For private listening.
- Operation/Battery and Reverse/Forward Indicators: Visual cues for device status and tape direction.
- DIR (Direction) MODE Button: Controls tape playback direction.
Maintenance Features:
- Service Manual: Provides detailed instructions for disassembly, mechanical adjustments, and electrical adjustments, including tape recorder section (head azimuth, tape speed, phase check) and radio section (FM frequency coverage, FM tracking, AM adjustment, AM frequency coverage, AM tracking, VCO adjustment).
- Safety Check-Out: Emphasizes performing a safety check after service, including AC leakage tests on exposed metal parts, with specific methods outlined (commercial leakage tester, battery-operated AC milliammeter, or measuring voltage drop across a resistor with a VOM or battery-operated AC voltmeter).
- Safety-Related Component Warning: Highlights critical components (marked with ▲ or dotted line with ▲ on diagrams and parts list) that are essential for safe operation and must be replaced with genuine Sony parts.
- Exploded Views: Detailed diagrams for cabinet (rear/speaker, front), and Deck A/B mechanisms (multiple sections) to aid in component identification and assembly/disassembly.
- Electrical Parts List: Comprehensive list of all electrical components, including semiconductors, capacitors, resistors, inductors, and switches, with part numbers, descriptions, and remarks.
- Semiconductor Lead Layouts: Diagrams illustrating the pin configurations of various semiconductors for correct installation and troubleshooting.
- Printed Wiring Boards: Layouts of the printed circuit boards for easy identification of components and test points.
- Schematic Diagrams: Detailed electrical schematics for the tuner and audio sections, including IC block diagrams, to assist in circuit analysis and repair.
- Correction-1 Document: Provides an update to the service manual, specifically correcting a part number for the "BUTTON (TU)" component (part No. 3-359-249-01 corrected to 3-359-249-11).
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