Aiwa HS-PX303 Service Manual

The HS-PX30, HS-PX303, and HS-PX900 were stereo cassette players manufactured in 1989 by the Aiwa Corporation of Japan. The power output was 15 mW (EIAJ) per channel through 16 Ω headphones. This service manual contains the circuit diagram, calibration specification, and information that would be useful for repair purposes.

Review

This was a high-end audiophile design where the electronic and mechanical engineering are extremely elaborate and advanced for the time. In this design they use a pair of integrated circuits (ICs) for the Dolby B/C function, hence there is a NJM2065AM IC for each channel. They also use the CXA1249M IC to provide the parametric DSL function, which was quite a feat of engineering during that time. For the tape transport functions, they used a system control and logic IC TC9311F-014, which also controls the solenoid (SOL1). The motor driver design is also elaborate with a 3-phase motor driven by NJM2613 IC, providing extremely smooth speed. The remote control design is a resistive ladder network type decoded by the BA3818F IC, which contains operational amplifier comparator blocks. Finally, the preamplifier and power amplifier functions, including channel switching, are achieved by the TA8115F IC manufactured by the Toshiba Corporation. The SMD version (F) had power dissipation of just 400 mW and typical quiescent current of 9 mA making it very efficient at 3 V operation. In these early ICs the power amplifier stages had fixed closed-loop voltage gains of 27 dB to keep THD to minimum, but still it sounds decent with a good pair of headphones. Hence 32 Ω coils will provide much better sound definition and resolution at the expense of power output.

For the tape transport design, Aiwa uses their alpha minus 2 (α-2) mechanism, which was one of the most reliable at that time and became the basis of many later designs by other Japanese manufacturers. In this design, a three-phase disc motor drives a pair of capstan flywheels via a single drive belt. The auto-reverse system consists of a program cam wheel, and solenoid actuation. The tape path consists of an amorphous head with bi-azimuth head alignment taking the engineering technology to extreme levels. The amorphous alloy usually exhibits high flux density resulting in exceptionally high playback fidelity.

Price/eBay

These cassette players are sometimes available for sale and the price can vary depending upon condition. It is a lovely piece of electronic engineering history that many collectors like to own, and a complete unit in mint condition together with its headphones, remote control, box and accessories can command a price in excess of one hundred pounds on a good day. Unfortunately, a broken unit in poor condition would not be worth much because of the compact construction, which makes it time-consuming to repair.

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