*** this instructable takes into account that you have some mechanical dexterity and some experience in disassembling consumer electronics ***
lalala music music KERCHUNK!
the lowly 8-track tape, abandoned long ago in favor of the cassette tape. they can still be easily found at thrift stores and flea markets for less than the cost of a snickers bar.
the 8-track was the first portable music medium that actually really took off. sure there were other portable formats but the 8-track was the first to win wide public acceptance and become a common option in automobiles of the 60's-70's. initially created by lear jet, the aircraft folks, the 8-track became popular due to its simplicity of use. 8-track tape machines found there way into portables, cars, and home stereo.
shove the tape in and the machine starts playing. you have 4 "programs" to choose from. they are musical programs and have nothing to do with computers. each program contains stereo songs. 4 programs each having 2 tracks since they are in stereo = 8 tracks.
let's learn a little bit about these tapes and how to revive a malfunctioning machine!
Step 1: How the Tape Works
the 8-track tape is a continuous loop tape so there is no rewind. the only options the consumer has is play, fast forward, record, and program change. some basic machines like the one featured in this instructable only offer play and program change.
the picture shows how the tape works. the tape is pulled from the center, out past the machine's mechanism, and then re-spools onto itself on the outside of the spool. the action of the tape being pulled from the center causes the spool to turn thus winding the tape back onto itself. what makes this work is that the backside of the tape, the side that doesn't have the music on it, is polished up with a dry lubricant to aid it in sliding out and over the spool of tape.
unlike most tape formats, the rubber roller called the pinch roller is part of the tape cartridge and not the machine. in the picture you will see the roller on the top right, the playback head in top center, and top left you will see what looks like two "J's" back to back. that is the sensing contact that causes the machine to automatically change programs as the tape is playing.
the tape has a foil splice in it. when the foil hits the contacts it trips the program change circuit causing the playback head to shift to the next program. changing programs can be left to the machine to do it automatically or you can hit the program change button and do it yourself during tape play.
the tape was divided up into 4 programs each equal length. this meant that songs had to be picked to equally fit into each program or you just let it ride and your music got interrupted by a KERCHUNK during the song as the machine changed programs. that's one of the endearing yet annoying quirks of the 8-track format.
Step 2: Let's Dig In!
the unit we are opening up is typical of the common low priced portables (pic 1) that were sold. millions of similar style players were sold and used ones can still be found out there in the wild for about the price of a value meal. this particular model is a panasonic rq-831a, am/fm 8-track player. it runs on batteries or 110v AC power.
turn the unit over and look for screw holes. some manufacturers were nice about showing you what screws to remove (pic 2) and which not to. in this case the screws to remove are marked by little arrows. the one not to remove has a big "don't remove me" warning stamped in the plastic (pic 3). the screw at the base of the antenna is typically one of the ones you may not need to remove as all it does is hold the antenna in place.
not all manufacturers were nice enough to tell you which to remove so you may have to use your best judgement. your goal is to get the case to split in half as pictured (pic 4).
Step 3: What's Inside?
so what are you looking at in there?
you should have a circuit board or boards, and a tape mechanism. first rule.. don't move anything!
some manufacturers used strange ways to link the dial scale to the tuning capacitor on the circuit board. on this particular model for example they have a plastic piece on the tuning capacitor (pic 1) that lines up with another on the front half of the unit (pic 2). if you move them, you'll have to finagle with them to get them to line up on reassembly. if you try to force both halves together, you can break things and make the unit not worth fixing. be careful!
in pic 3 you see the power transformer and some of the power supply capacitors. the large caps immediately near the power transformer could be your culprits if you have a unit that seems to work ok but has an obnoxious hum no matter what the volume control is set at.
in pic 4 you see the tape mechanism. you will be removing this.
Step 4: Removing the Mechanism
the tape mechanism on these portables will typically be screwed down to the plastic case by just a few screws (pic 1). this machine has 4 screws to remove to liberate it's mechanism. once the screws are out, carefully lift the mechanism out and lay it over with the belt side up (pic 2). you might have to remove some wire ties in order to get enough play on the wires to move things around.
Step 5: Checking Out the Mechanism
8-track machines are amongst the simplest of tape machines. the transport has 1 belt. unless the machine was recently serviced, chances are your belt will be in one of two states.. melted or stretched. a melted belt looks like tar. see my instructable on rebuilding a norelco cassette recorder for details on how to deal with a melted belt. be very careful with the tar like residue from a melted belt. it gets on EVERYTHING.
to check for a stretched belt, hold the motor pulley without touching the belt and try to turn the flywheel. it should have quite a bit of resistance to slipping. if it just slips around the motor pulley, your belt is stretched.
despite the size and appearance, a rubber band is NOT the proper fix. will it work? yes but will result in very noticeable and annoying speed variations as the tape plays. the proper fix is a proper belt. my belt supplier of choice is ebay. since i fix lots of old tape machines, i purchase universal kits that look like they may have what i need. after purchasing a few of those kits you end up with a good stockpile of belts for future repairs. you can buy just the belt you need from specialized suppliers but you'll pay almost as much for that single belt as you will for a universal kit.
Step 6: Lube and Clean
all machines eventually need some TLC.
what to lube?
sewing machine oil will be adequate for this step. (pic 1) one drop on the motor shaft where it enters the housing. one drop on each bearing contact on the capstan shaft. the capstan shaft is what has the big flywheel attached to it. most decks have two bronze bearings to support that shaft. get one drop onto each bearing. on some decks, the flywheel may have a retainer plate to keep it from flopping out. one tiny dab of white lithium grease where the retainer plate contacts the flywheel is all that's needed.
the head on an 8-track machine raises and lowers via a stair stepped cam mechanism that's actuated by a solenoid. most of the time that mechanism is fully accessible. you will see a solenoid that tugs on a mechanism that trips a cam causing the head to move a notch. once the head has stepped up three times, it drops all the way down and the process can repeat. a tiny dab of white lithium grease on the cam steps and on any other sliding metal parts is all that's needed. a q-tip makes a great applicator for this.
what to clean?
clean off any oil that inadvertently got on the motor or flywheel pulley. if need be pop the belt back off and give it a wipe to make sure its clean. clean off any grease that might have gotten on any parts that can contact the tape. tapes and grease don't mix.
next you'll need some denatured alcohol and q-tips.
you need to clean the head, capstan shaft, and tape sensor contact (pic 2). the capstan shaft is the metal shaft that turns when you spin the flywheel. spin it and clean off any oil residue from when you lubed it. use a dry q-tip for this. once that's done, dip a q-tip in denatured alcohol and repeat the spin and clean process. you don't want any oil residue on this part where it can get on the tape and ruin it.
next clean the head (pic 3). the head is the silver metal block in the center. this is what reads the tape. clean off any brownish residue. brown residue is usually tape oxide that has worn off and accumulated on the head. leaving it on there will cause muffled sound. use a q-tip dipped in denatured alcohol to do this.
next, using another q-tip dipped in denatured alcohol, clean the tape foil sensing contacts (pic 4). these may also have brownish tape oxide on them. if these aren't clean, program change may not happen automatically.
for the last bit you'll need electrical contact cleaning spray.
clean any volume or tone controls you can get to. using electrical contact cleaner, find a spot where you can get a shot into the potentiometer. once you give it a shot, work the control back and force a few times. this should clear up any scratchy controls the unit had. do this for any switches you can get to as well. you're already in the unit, might as well do it.
Step 7: Other Issues to Take Care Of
on portables, your biggest enemy is battery leakage.
battery leakage shouldn't be an all out deal breaker if you're out looking for a used unit. it can work to your advantage actually when negotiating with the seller. look at the leakage. which way does it appear to have gone? if the unit sat upright and the batteries where at the bottom, there's a good chance the damage is limited to just the battery contacts. the rusty trail of leaked battery chemicals should tell you which way the unit was laying when the batteries finally gave out.
in the case of this unit, the leakage was limited to just corroded battery terminals. something that cleaned up easy with a brass brush and some wd40.
what are worn heads?
in pic 2 you see a worn head. this isnt an 8-track machine's head but the concept is the same. note how the center of the silver metal block looks like someone sanded it unevenly? that's what happens to tape machine heads as they wear. the surface of the head should be even and smooth across its entire face. see pic 3 for what a practically new head looks like.
what will a worn head cause?
degraded sound quality. normally this is a huge issue for tape enthusiasts but portable 8-track players didn't exactly have the best in sound to begin with. a worn head is a bad thing but don't let it be a deal breaker on a cheap unit. if you're only spending a few bucks, go ahead and give it a whirl. you don't have much to loose. if you're paying more than say $10 for the unit, open the tape door and look inside. you want something that resembles the condition of the head in pic 3 as much as possible.
Step 8: Reassemble and Enjoy
put the unit back together and enjoy it!
when looking for used tapes, keep in mind that the part of the tape that's been exposed may have a dropout in the sound level from all those years of sitting there exposed. that's to be expected. it's not a flaw in your machine, it's just an old tape.
here's a tip when you're out shopping for used tapes. look at the end of the cartridge where the tape is actually exposed. poke at it with your finger right in the center. there's a foam rubber pad under the tape that's supposed to be springy. that foam is usually missing or dry rotted. dry rotted foam will crunch when you poke at it. it's common to find 8-track tapes in this condition. they will still play but sound quality will suffer. some really nice 8-track tapes actually had a spring mounted felt pad instead of foam rubber. those tapes are uncommon and worth getting if you find them.
you can rebuild the failed foam rubber pad. there are articles online on how to repair the pressure pad on an 8-track tape if you're up to it.
into old tech? follow me on instagram as vintagetechguy to see random pics of interesting old tech.
want to learn more about tape? check out the tapeheads website!