basically what you are dealing with, are old units. they don't make them anymore. what i'm referring to are the single unit, one piece construction, single deck machines. to me those are kinda the coolest ones. like the panasonic 5000 series, a personal favorite of mine. however the early attempts at the three piece unit {detachable speakers} are still kinda cool. my favorite jambox of all time is of this ilk {sanyo c 30}. however usually i prefer the one piece. i would never buy a jambox with a cd player in there because that is really uncool. single deck, one piece, no cd player. hopefully with aux ins/outs.
there are all these "holy grail" models that i would probably just stay away from. those are "collectable" items that are too expensive typically. {i just want to jam i don't want to impress anyone.} instead, you should look for a good basic working jambox in the 50 dollar range. i wouldn't jump into an 800 collector model for the first one. look at a lasonic brand monster on ebay. those things cost a fortune. badass, but expensive. {no no no no NOT the ipod one.}
here's what typically will be wrong with older jamboxes:
a. belt issues. when powered up, if you hit play and the little wheels won't spin, yet you can hear the little motor going, usually that means there is a loose or broken belt. this represents the majority of cassette player malfunctions. it's not a very difficult repair, however sometimes getting the jambox apart is really hard. they were made to sell not fix. if you are fairly handy, learning to do this would be a good idea if you want to get them cheap, fix them and offer them to your friends or whatever. usually when the playback is slow, the belt has stretched. you can download repair manuals and find info on the net to fix. you kinda need a bench and some badass light. and lots of screwdrivers of various sizes and lots and lots of patience. if you learn to do this simple repair, you can buy badass units all day long and fix them really cheap. it's not quite as easy as it sounds as they can be really hard to take apart and put back together again. jamboxes weren't really made to open up.
b. button/knob issues. sometimes you will hear crackles and stuff when you turn the volume up or down or move the selector or whatever. over time, the contacts will oxidize. there are two types of sprays you can buy. one for metal to plastic contacts, and one for metal on metal. if you don't know which switches need which spray, stop. typically the unit will need to be taken apart to really get to the potentiometers good.
c. jack issues. the headphone jack may not work. the proper spray often fixes them right up. sometimes if a unit won't make sound but the mechanism seems to work, you can clean the jack for the headphones, and it may then be able to pass signal to the speakers and start playing. the little audio cut-out device in there that turns the main speakers off when the headphones are plugged in can get dirty. easy fix.
d. head alignment issues. this is a tough one without the proper gear. i would pass on this one.
really your best bet is to get one that already works. remember these things are more than thirty years old. so over time, the rubber and resin bits will dry out and sublimate. but you can still find units that work. that's your best bet. just get one that already works pretty good. clean the battery compartment, perhaps with some fine sandpaper on the contacts, clean the heads, demagnetize them, and treat the rubber. you can research how to do all that stuff. it's really easy and cheap to do and will fix about 40% of the problems roughly speaking.
here's what to test for. make sure it powers up. check the battery compartment. for some reason knuckleheads will leave those batteries in there for years and they will corrode all over the place. {i've even had guys ship me jamboxes with ten of those big dead corroded D cell batteries still in there. probably would have cut the shipping weight in half to remove them.} it's nice if the battery contacts are super clean. pop a tape in that you know works and you know what it sounds like. hit play. it should play full range out of both speaker sides. move the balance knob back and forth. both stereo sides should sound the same. if there are woofers and tweeters make sure they all work. sometimes this can be just a lose wire, if one of the speakers isn't functioning. overall the knobs should move and properly affect the sound without crackling. though, from sitting around, they likely will make noise. some of this will go away with use, or it may have to be cleaned. again if it pops badly, you might want to pass on the unit as it will need to be taken apart. check the FFW and REW and see if it works. the tape should move quickly and smoothly. any issues here are likely belt stuff. make sure the cassette door opens smoothly. they lube the pivot at the factory and that will dry up after a few decades. that is a super easy fix. heck i have a couple jamboxes where i just have to help the door a little bit when changing the tape and it's no big deal. i have a unit that doesn't rewind that great, but i don't care i just keep playing it. part of the deal of cassette over mp3 is that you kind of listen straight through anyway and don't do much rewinding. {have you ever noticed that most folks rarely listen to a whole song on an ipod before they change the song. please stop doing that. about the time i get into the jam, they'll switch the song. arthur "no guitar boogie" smith.}
that's about it. the best deal is if they work already. if there's a little bit of crackling with the knobs, it maybe plays a tiny bit slow, and there's a slight hesitation on the FFW or REW, don't despair. if it's a cool unit you really want and it's cheap go head and get it. i have purchased units like this that continued to work for years.
now about ebay. it's a real crap shoot. i have bought units off there from guys that had a real high rating and they guaranteed the unit to be perfect, and it showed up and would not play. more than once this has happened to me. so be warned about that. if you go back to the seller, they get all sheepish, "well it played when it was here la dee dah". so i assume that if i buy four units off ebay, only one is going to be in great working order. one will need some minor work and two will need lots of work. even if the rating is high and the guy assures you they are all perfect. i speak from experience.
your best bet is to find them in the wild {pawn shops, garage sales, thrift stores…hey while you are there, buy a bunch of tapes}. that way you can test before committing your hard earned dollars and/or time. never let a good one that works get away. ask your friends and family about them. if someone has one, lots of times, they never use it and you can just have them. i repeat, never let one that works get away. if you find one, buy it.
repair places. i have never found a place that will work on units that aren't backlogged for months, and staffed with unfriendly guys that do NOT want to work on those things. they typically will try to talk you out of the repair and/or quote you some really high price to make you go away. if you find a place that's worth a damn, please tell me, i don't care what state it's in.
you will most likely have to find them in working order and/or undertake minor repairs thyself.
