Sharp RT-3151

The RT-3151 (also known as RT-3388A, and RT-3151E) was a stereo cassette deck manufactured by the Sharp Corporation of Japan. Coined "Electronic Tape Processor", it had Automatic Program Locate Device (APLD) that detected the silent gaps between recordings. The microprocessor module was essentially just a quartz clock with timer facility and liquid crystal display. This allowed the tape deck to switch ON automatically at a programmed time to play or record. One nice feature was the full auto-stop transport mechanism, which came to a stop on rewind and fast-forward modes as well.

This tape deck was one of the earliest with a hall sensor (A), which detected the change in magnetic field as a circular magnet (B) rotates. This provided additional safety for the tape because the computer system would bring the unit to a complete STOP if the tape-winding spindle stopped.

I thought this cassette deck had an interesting design in that the mechanism for fast-forward, and rewind functions used toothed cogwheels, however a tiny pulley with rubber surface drives them! When this rubber surface wears out, you can expect the forward and rewind functions to struggle.

Another interesting design feature is that they use a rubber-surfaced pulley wheel (D) for driving the triple-edged tape-winding cogwheel (C). Its top edge is for the drive belt that rotates the magnet (B), the second edge has cogwheel teeth for the fast forward operation, and the third edge meets pulley (D).

One of the wonderful things about this cassette deck is the superb sound quality that exhibits very sharp treble and low bass. Even with a worn head it sounded good, which led me to believe that this deck deserves to have a more special high-end head. The circuitry is also interesting as it has RH-IXO437AFZZ integrated circuit (IC) preamplifier that also performs some filtering. It then feeds another IC, which is VHIP-646. Many of the stages have extremely precise LCR filtering which is the reason for so many coils in metal enclosures. Electronically, this seems like a very high-end audio circuit design, with a basic audio head.

Cost/eBay

This unit has excellent audio reproduction quality that you can hear directly from its headphone socket. It has remarkable bass and treble response, and therefore a good working unit without any issues, in excellent condition, can cost well over one hundred pounds. However, a worn out unit can be time-consuming and expensive to repair. The replacement parts are difficult to find and expensive if you are lucky enough to find them. Therefore, a broken unit would cost approximately thirty pounds depending upon the type of fault.

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