I've had several boomboxes, all of them long gone (cassette decks went West, one cheap GPX box having quit after only three weeks [!], and they were not, in my opinion, worth repairing). However, I found a Panasonic boombox a couple of years ago near the trash barrels behind my apartment. The cassette deck worked for a short time, then quit; however, I think I know what the trouble is: a loose, stretched or broken drive belt. The radio works quite well, even though the FM antenna is missing.
Haven't had the box apart to look at the problem yet; oh well, one of these days.
(Maybe, and I'm hoping this is the problem, the belt just slipped off a pulley, but I think it's a bit more serious than that.) It should only take a few minutes to diagnose the trouble, but if the belt is broken, I don't know if I could find replacements anywhere, as no one much uses boom boxes any more since the advent of CDs and mp3s. Ask a teenager today if he or she knows what a boom box is and you might well get a blank stare, a shrug and a surprised "What's that?", since today's kids have iPods and, in many cases, are wrecking their hearing listening to them with earbuds at extremely high volume.
I know there are (or were, until recently) boom boxes made with CD players; my barber here in town has one in his shop, but the CD deck doesn't work. Doesn't bother him, though. He keeps the radio set on a news-talk station in Cleveland most of the time.