Magnavox D8347

The Magnavox D8347, also called the Philips D8349 Cu-Booster, was introduced in 1985. It measures 530 x 160 x 185 mm. It has 6 speakers (four 4" woofers and two piezo tweeters) and a 3-band graphic equalizer. It also has RCA input jacks selectable for Line In or Mic, but I couldn't get either of them to produce any sound, even when the Record key was pressed. I've had the same problem with a couple other Magnavox models, and I don't understand it.