Savica FM receiver

16.03.2007 23:44

Savica was an old solid state AM and FM radio receiver made by Iskra some 40 years ago. Originally it had only a mono receiver for middle and short wave and VHF bands. Interestingly this one (from my uncle) was modified by my father to also receive stereo FM broadcasts. I hear that this modification was quite popular at the time when first Slovenian radio stations began to transmit in stereo and more modern receivers either weren't available on the market or were very expensive.

Savica was particularly suitable for such a modification because the original FM detector had enough bandwidth to receive the entire stereo signal (which is encoded above the normal 15kHz of the audio signal). This meant that the original circuit could be left mostly untouched, only the original mono audio amplifier was replaced by a stereo decoder and a pair of amplifiers.

Savica front plate

Names of public middle wave broadcasts are permanently written on the front plate. Who needs RDS?

Savica front plate

Most of the original audio-frequency electronics is at the back of this picture. The audio amplifier is built with discrete silicon and germanium transistors. Power supply consists of a couple of diodes (probably a half-wave rectifier) and a large silver capacitor on the left.

Original electronics

This is the custom-built stereo decoder using the RCA CA1310 chip. The original FM detector is in the metal box in the lower left corner.

Update: the metal box actually contains only the the radio-frequency part of the FM receiver. The detector is on the main circuit board on the first picture.

Stereo decoder

And here are the two audio amplifiers, one for each channel. The two large capacitors on the left died and had to be replaced. This was the only repair needed to bring this old machine back into service.

Stereo amplifier

Posted by Tomaž | Categories: Analog

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