Vintage Sony Portable Cassette Player Radio Player Boombox CFS-D7 – For Parts. Cassette does not work, for restoration or parts only. The Sony CFS-D7 is. Notable for featuring advanced digital tuning, which was uncommon at the time. Key Features and Details. Digital radio tuning display. Part of the high-regarded Sony “SIRI III” series. Built-in stereo speakers with a balanced, warm sound. Known to require cassette belt replacements for proper function.