The D1720 was a pocket radio manufactured in Hong Kong by the Philips Corporation. In its time, during the late 80s and early 90s, it was an ultra thin AM / FM stereo radio, with ultra light headphones. It was approximately 12 mm thick and took a pair of “AAA” sized dry cells to operate. It had volume control sliders for each channel, FM stereo LED indicator, band selector switch, and a power switch. A miniature variable capacitor performed the tuning function for both bands. The radio usually came in silver, black, red, and yellow. The yellow one was part of the Philips “Moving Sound” range.
For the headphone amplifier, this radio utilises a pair of TA7688P integrated circuits (IC) manufactured by the Toshiba Corporation. It is probably one of the best ICs used in walkmans and high-end stereo, and the sound quality is excellent. If you ditch the supplied headphones, and use something like the Sony MDR-W15, then the sound quality will dramatically improve.
This radio has such a simple design with elegant curves and lines, and for it to be appreciated you need to see it from all angles. Even though the case is plastic and manufactured in Hong Kong, a nice one without scratches would look great.
In this multi-page article, you can see some of the electronic design features, and how they used conventional components to make it.
I just love these wonderful volume control sliders, where each channel has an independent slider control.
Cost / eBay
These were mass-manufactured however being so popular people usually used them until the headphones broke or they bought the next belt-on gadget to take its place. The price can vary from as little as five pounds upwards, and depends upon the day and the number of radio enthusiasts interested.
I have never had much luck with this one, because the first one I bought had water damage and rust, and the second one had PCB damage from battery electrolyte. I should have enough parts to make a good working one soon. :-)
This Article Continues...Philips D1720
Philips D1720 inside View
Philips D1720 Tuning Capacitor and Ferrite Coil
Philips D1720 Components
Philips D1720 Vintage Headphones
Philips D1720 Battery Compartment
Philips D1720 Box and Packaging