Panasonic RQ-SX75

The RQ-SX75 is a stereo cassette player manufactured in Japan by the Panasonic Corporation during 1998. It was one of the smallest compact cassette players with dimensions 75.8 mm × 108.6 mm × 20.9 mm, and mass 171 g with rechargeable battery RP-BP62EYS1. This unit can also operate with a standard AA size dry cell, which fits into a special battery holder RFA0617-H that attaches to the side of the player. The rechargeable battery provides 16-hours operation, whilst an alkaline battery provides 54-hours operation. The unit can also operate from both power sources providing a total of 70-hours operation time. Here are some of its features.

• Automatic reverse mechanism
• TPS (Tape program sensor)
• One repeat, Intro-scan, blank skip
• Dolby B noise reduction
• S-XBS (bass boost)
• Battery indicator
• Illuminated remote control

Review

This early design by the Matsushita Electric Corporation was one of the nicest that most audiophiles tend to like. It is packed with a vast range of integrated circuits to bring you all the features. However all of this microminiaturization comes at a cost. They had to use a special dedicated microcontroller for the mechanism control (M34561M6063F). The Dolby B function is provided by another IC (NJM2185AVTE1). The disc motor is yet another extremely elaborate controller IC. Finally the preamplifier and power amp IC is the famous BA3632KE2. In order to power all of these integrated circuits from just 1.5 V, they had to use a DC-DC converter IC (BA9750FVE1), which produces a 2.2 V rail.

The disc motor and its driver IC produce an extremely smooth speed which is noticeable straight away. With 50 Ω impedance headphones one can expect 2.5 mW (rms) audio output. Providing you have a high-quality pair of headphones, you can expect extremely good sound.

Price/eBay

The RQ-SX75 sometimes comes up for sale at the auction site and the price varies depending upon the condition. A unit in good working order in its original packaging and mint condition can fetch around a hundred pounds on a good day. Unfortunately a broken unit in bad condition would not be worth much. In this unit the tape transport mechanism consists of two drive belts that are beneath the PCB. Therefore to replace the belts, one has to desolder the board from components attached to the transport mechanism, and this is time-consuming. In addition, this unit has the common problem of the spring retaining disc (in the clutch mechanism) popping off. Unfortunately, there is no original replacement part available for this. In the past I have been able to repair the clutch mechanism by using an e-washer to secure the spring, which is a time consuming modification. Consequently a broken unit that requires repair is usually not worth much as repair costs will be high.

I managed to find a unit that needed new drive belts and spring retaining disc, hence the rest of the pages in this article are my photographic notes which might help anyone repairing theirs.

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