Sony WM-FX251

Sony WM-FX251

The WM-FX251 was an AM/FM radio cassette player Walkman manufactured by the Sony Corporation of Japan in approximately 1997. It had a PLL synthesized tuner with a liquid crystal display (LCD), and was capable of storing 15 FM stations and 5 AM stations. It had automatic volume limiter system (AVLS), and a bias selector for metal/chrome and normal tapes. It has four integrated circuits (IC) requiring two “AA” sized dry cells to operate providing 22 hours of operation time. The power output through the supplied MDR-023 earphones is 5 mW per channel, and it is capable of delivering up to 8 mW per channel through other headphones. This cassette player is 115 mm × 90.5 mm × 34.4 mm in size and weighs 245 g with batteries, tape, and earphones. It does not have auto reverse, as they have used that space for the radio circuit, however it does have a stepper motor. It has an interesting design in that it has no plastic belt clip, but instead comes with a leatherette carry case, which has a belt strap.

Sony Walkman

Radio Buttons


Headphone Socket and Switches

This player has a very advanced chipset achieving remarkable operation times with just a pair of batteries. It has the LB1979, TA8122AF, LA4582C, and NEC D17015GS, integrated circuits, which amounts to a huge number of transistors, for a 3 V Walkman.

Although the cassette player design is average, lacking an auto reverse, it does have a stepper motor for the tape transport mechanism providing a super smooth speed. The radio design is also something special, because this FM/AM radio circuit requires very few tuning coils and capacitors, and yet operates on 3 V. A synthesized tuner also requires a certain amount of digital management, and the engineers at Sony Laboratories managed to pack all of this circuitry onto a single board. Usually, conventional radio circuits this small did not work well in the 90s, however this one works well, the reception is clear and the tuning is sensitive. Programming the presets is straightforward but requires getting used to, however eventually one realises the logic behind the method.

Cassette Compartment
Power Socket
Tape Functions

Tuner LCD

Cost / eBay

This was an iconic design during the late 90s. It has an ergonomic ABS plastic case, with a shiny futuristic finish. Many people will remember seeing a button layout like this, which was popular for a while. It would have been mass-produced, and there should be plenty out there, with Walkman collectors. I managed to get my reference model together with the box, manual, and carry case for around ten pounds. Unfortunately, the seller had thrown away the original earphones, so I had to test it with another pair.

These units usually require a change in drive belt, as it becomes loose after all these years, however, the good news is that a generic belt is readily available, and simple to change.

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Sony WM-FX251
Sony WM-FX251 - How to Open
Sony WM-FX251 inside View
Sony WM-FX251 Audio IC
Sony WM-FX251 Radio Design
Sony WM-FX251 LCD and Synthesized Tuner
Sony WM-FX251 Audio Head and Tape Mechanism
Sony WM-FX251 Tape Transport Mechanism
Sony WM-FX251 Step Motor and Driver IC
Sony WM-FX251 Power Supply
Sony WM-FX251 Cover
Sony WM-FX251 Box