JVC CX-R7K Service Manual

The CX-R7K (also known as CX-R7) was a stereo cassette recorder with AM/FM tuner and auto-reverse, manufactured by the JVC Corporation in 1986, in Japan. It had full-logic transport mechanism consisting of two miniature motors, Dolby noise reduction on playback, and metal tape capability. These early units took the electronic engineering to extreme limits, and consequently this unit was high-end for the time.

The design of this unit is rare because it has two motors in the transport mechanism. There is an actuator motor (TWS-154) that controls the mechanism including the auto-reverse system, whilst a second motor (FN26CA) drives the capstan. The electronics for the capstan motor was very elaborate as it used a pair of LA5524M integrated circuits (IC) to govern its speed and direction. The control of the transport mechanism required a microcontroller (M51556P) and a plethora of SMD transistors for the drive logic.

The tuner circuitry consists of TA7792F IC, which provides the AM/FM IF detection, whilst the TA7373F IC provides MPX functions.

The audio circuitry consists of BA3412K IC, which is a complete package, providing playback and recording functions. However, they still had to use a LA4535M IC for the power amplification to drive a pair of headphones. In addition, the Dolby noise reduction function requires another dedicated IC (BA1102F). It is remarkable that all of this electronics operates on as little as 3 V from a pair of AA size batteries.

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