Sharp RD-620

The RD-620 is one in a series of mono cassette recorders consisting of RD-620D, RD-620DS, and RD-620DB, manufactured in the Philippines by the Sharp Corporation of Japan. It is a mono portable cassette recorder mains and battery powered. It has built-in 6.5 cm loudspeaker that will provide approximately 600 mW (MPO) audio output on mains operation, and 350 mW (RMS) on battery operation. It has built-in microphone, and a jack sockets for external microphone and earphone.

Review

In the evolution of compact cassette recorders, we are looking at a much later design when manufacturers started utilising plastic parts in the tape transport mechanism, and integrated circuit technology for the electronics. In this design, they use a plastic pushbutton assembly and consequently one has to be careful using it as any heavy-handedness can damage it. They also use a BA526 integrated circuit which reduces the component count drastically. This IC is a single-chip tape recorder solution with built-in preamplifier and power amplifier. Interestingly, this model has a single motor and there is no servo drive or any other circuitry except a simple connection to the power rails. On the printed circuit board (PCB), it has the following ICs and transistors.

• BA526
• 2SC1815GR

In this model the playback and erase heads are P5407, P5406 respectively. The Mitsubishi 6 V DC motor is MMI-5B6RKF. Providing these and the drive belts are in good condition, the sound will be fairly good, as these vintage tape recorders go. Many people will remember listening to one of these in their youths and will want to relive that time again listening to old songs.

Price/eBay

It goes without saying that it is a basic budget-end model with basic functions, and it would have been mass produced very cheaply. The number of survivor models is dwindling and therefore it might increase in value in the very distant future. A broken unit in bad condition is not worth much, however a unit in mint condition in its original box with manual could fetch a small packet on a good day.

I was lucky to get this in the spares and repairs section, and it was in fairly good condition apart from a broken pinch-roller spring. It was broken from the long end which pushes the roller onto the capstan. I simply undid some turns from the same spring to make a new long end and it worked! In the following pages of this multipage article, you can see photos of the inside electronic engineering, and a closer look of the heads and motor.

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