This Sony radio cassette player was a Freecycle find. Besides needing a clean it appeared in good condition and had clearly been sitting for some years after its teenaged former owner moved onto pastures new, and left the cassette format behind. Though no competition for models made at the height of the boombox’s popularity, it was second from the top of its model range at the time.
It had twin tape decks, one with recording and one playback only, and an FM/AM radio with fine tuning. You even got high-speed dubbing, a tone control and a lot of power for its small size.
Note the past tense in the previous paragraph, as (spoiler alert) this was ultimately scrapped. I had intended to fix up the cassette decks and then add Bluetooth and an aux input to bring this device into the modern age with its retro charm intact.
The cassette mechanisms however were not Sony’s finest hour. I believe they are a design of Sony origin, as I’ve only seem them in Sony products. If you look inside a boombox from the ‘80s, you’ll probably find a mechanism lifted straight from the hi-fi decks of the day. Things were cheapened considerably in the ‘90s and by the turn of the millennium it’s a wonder they bothered producing these things at all.
The mechanisms in here had poorly machined plastic flywheels fitted off-centre on the capstan shafts, and were constructed almost entirely of plastic parts.
Plastic, unfortunately, becomes brittle with age and this was the case here. As I delved into the repair, replacing the 4 belts, plastic pieces were breaking regardless of how careful I was. Clips started to snap, and just pushing the buttons was enough to break the various linkages and sliders that actuated the heads or moved the reel drive into place against either of the take-up reels.
The recording deck used a permanent magnet erase that, rather than swinging out of the way, was permanently hovering above the tape. Though it wouldn’t engage the tape unless the record function was pressed, it was close and strong enough that it would quite easily begin to erase any tape in playback. I wouldn’t be surprised if some treble loss was noticeable after a tape was run through one of these units a few times. The head itself had no adjustment what-so-ever for alignment or azimuth, and was clipped into a plastic holder – which, as expected, broke.
This unit was scrapped for parts, but I thought it worth taking a look at as cassette decks aside it is otherwise a nicely built unit. On the left is the shielded mains transformer.
In the middle is the main board containing the AC rectifiers and DC power supply circuitry, the amplification, line preampfification and the tape playback and recording preamplifier.
On the right sits the tuner which is an independent module. The tuner in particular performed very well. It is based on Sony’s CXA1238S single-chip FM / AM tuner. The operation of the tuning dial is choppy as is common to virtually all DSP-based tuners, but when it locks onto a station it does so with minimal background noise and a clear sound. Even the AM section is very good, appearing to be of fairly wide bandwidth and supporting short, medium and long wave bands. This is a self-contained module and may well make an appearance in a future project. A ‘50s era replica analogue radio perhaps.
The mainboard is nicely labeled, something you don’t see in modern units. The amplifier chip is a Sanyo LA4598, which outputs just shy of 3 watts per channel at 9 volts. The tape playback and recording preamplifier is a BA3423s. Most other functions are handled by discrete components.
I salvaged the speaker drivers among other components. These were used in many Sony boomboxes of the day and are actually very good. There were also piezo tweeters that do very little and hence were left behind. They’re more like super tweeters as their output level is so far below that of the main speakers it is all but impossible to hear them unless in isolation.
I kept most of the chips and components, the tape motor, the tuner module and the power transformer. Maybe some of these parts will be seen in upcoming projects. If you find one of these and you want a very nice sounding portable analogue radio, you can’t go wrong. I’d avoid playing any decent tapes in the recording deck unless you remove or demagnetise the erase head first. They’re great candidates for Bluetooth mods, though an ‘80s unit would be arguably more worthwhile for this purpose if ‘retro’ is what you’re after.
