Servos for Rapid Cassette Handling and Tape Threading in a Quadruplex Cassette Recorder
Reginald W. Oldershaw · Journal of the SMPTE · 1972
Some aspects of the Ampex Model ACR-25, an automatic cassette VTR using the broadcast 2-in quadruplex format and holding 24 cassettes in a circular carrousel, each with a capacity of up to 6 min of tape, are described. The carrousel is mounted between two vertical transports, and a cassette from any bin location can be selected and injected into either transport. While one transport is playing, another cassette can be located and automatically threaded into the other transport ready to take over. The switch occurs during a vertical interval, so there is no discontinuity of picture. An important feature of the machine is the ability to play spots of 10-s duration. In this 10 s, it is necessary to rewind the tape into the cassette, return it to the carrousel storage area, select a new cassette, and thread and cue before the previous tape has finished playing. Described in some detail are carrousel and tape-reel servos which are important factors in providing this rapid back-to-back operation. The servos described for cassette handling use only fundamental principles and require no routine adjustments. Loop gains can be held to within 3 dB.