50-Year-Old 8-Track Changer Repair And Hack

For reasons still unclear, [Techmoan] has procured an RCA 8-track changer that holds five tape cartridges in a custom carrier. It somewhat works, but had a bit of mechanical issues here and there which needed some maintenance. Additionally, the player is designed for the US market and 60 Hz mains, but [Techmoan] is in the UK with 50 Hz.

Although electronics are used for the basic tape player portion, everything else is operated by mechanical gears, levers, and motors. The system plays both sides of each tape cartridge through to completion, and then switches automatically to the next one in the stack. Cartridges could be up to 90 minutes each, making for over seven hours of playing time. Oddly, the system does not repeat automatically after the fifth tape ends –operator intervention is required. It’s not entirely clear whether these carousels were primarily intended to play background music inside businesses, or built for niche consumer applications.

After discovering there was no setting to adjust the tape’s speed for 50/60 Hz operation, [Techmoan] could have ordered or fabricated a larger-diameter pulley for the motor drive shaft. But in true hacker style, he instead solves the problem with cellophane packing tape. By trial and error, he builds up the pulley diameter by winding lengths of tape until the music sounds just “good enough” to his ear. Then he pulls out the wow and flutter meter to really zero in — and gets it bang on. He says that this changer is needed for a future video, so we’re looking forward to see how it will be employed.

If you like these old mechanical logic controls, check out the video below the break. If you want dig into the workings of an 8-track player, check out Jenny List’s retro teardown from 2017.  Does anyone still use 8-track tapes any more?

27 thoughts on “50-Year-Old 8-Track Changer Repair And Hack

  1. 8-tracks don’t have “both sides” like a cassette tape. It’s one continuous loop with a marker indicating the tape has returned to the start. This signals the tape head to move down a notch for the next track (or pair of tracks for stereo), or back up to the first if the last track is done.

    1. …thus, the name “8 track” = four tracks of two channels.There is IIRC, a strip of conductive foil at the start of the program material/splice in the tape (it’s an endless loop – feeds from the center, takeup on the outside) Every time that conductive foil passes a pair of contacts, a rotary solenoid steps the head one track. It does this with a stepped wheel, which resets the head to the starting track…so it should be able to play any cartridge continuously if it’s a standard 8-track transport.

      How do I know all this? I took one apart as a kid. Bonus: the 8-track was invented by the inventor of the Lear Jet.

      1. He modified the already existing 4 Track tape. Doubled up on the number of tracks and put a pinch roller in every cartridge to simplify the mechanism. 4 Track tapes have a big hole in the bottom side for the roller, which has to lift or pivot into the cartridge. The hole made it easy for dirt to get inside the cartridge.

        Having a pinch roller in every cartridge made them cost a bit more, and the quality of the roller depended on how much the manufacturer wanted to spend. I recall some that had hard plastic rollers and didn’t play very well.

        Where a 4 Track tape had to be kept in a sleeve to keep it clean, an 8 Track could be protected by a simple piece of extruded plastic that clipped over the exposed tape end.

        One more smart thing Lear did was to not change the exterior dimensions of the cartridge. That made it possible to have players which could play both 4 Track and 8 Track tapes.

      2. I did the same thing (well took the 8-Track cassette apart) as a kid, then I spooled it on a reel and played it on a reel to reel tape player, it’s better to listen to two tracks at a time.

  2. Dang, ease up on the 8 track stuff :-D I saw an 8 track to compact cassette adapter on the weekend, and was actually contemplating buying it to screw around with, before the hind brain saved me with “Run! Flee! Hackaday are using specific patterns of pixels to hex you, what are they called again front brain?” “Words” “Yah, them damn sneaky word things, they get in your head. Creep up on you in the night…” “Okay, shut up hind brain, we got it.”

    1. In the mid-seventies I thought 8 track would be great for saving programs from a computer. Until I.learned about them and there weren’t 8 tapeheads.

      I have never held an 8 track tape in my hands

      1. On a per program basis, better seek times than a C90 with one per tape track, vs a bunch on one longass tape, but beyond that, oh and maybe better speed regulation, not much advantage.

          1. Exactly. And IIRC, they were prone to jamming. Also about 3x the size of the cassette = fewer bands in your glovebox (or the back seat was full of 8-tracks when you wanted to use it for something more athletic

      2. I also briefly entertained this notion. It was a time when a floppy controller and two drives cost as much as the rest of a hobby/home computer, so cassettes were the main mass storage device. Which was a poor choice because these required manually rewinding, and if you had more than one program or data file on a cassette, manual fast-forwarding as well. My idea of a solution was to buy two 8-track players that were on deep discount somewhere, and try to make them work like floppy drives.

        8-track tapes had features that made them somewhat suited to this:
        1) they were continuous-loop, so like a floppy, the computer just had to wait until timing signals indicated it was at the right “sector” to read or write a block, which directly corresponded to what it had to do on floppies (or indeed, hard drives),
        2) they had multiple tracks which the computer could “seek” to, just by activating a solenoid for half a second or so, which reduced the average access time.

        Still, since the standard tape size was about 40 minutes (long enough to fit a typical vinyl album), this meant that the loop took 10 minutes to get through, since there were four track pairs. I had two solutions for that:
        1) cut the loop length to something more acceptable,
        2) put a larger pulley on the motor to run the tape through at 3x the normal speed.
        Together, these got the maximum latency down to about two minutes, which was still ridiculous, but in the neighborhood of what it took to find a particular program on a cassette.

        Alas, I had to put this project on the back burner, as I was changing jobs and changing states at the time (geographical states, not physical), and by the time I had some time to spend on projects like this again, floppy drives had come down in price and the writing was on the wall already for cassettes.

      3. Sir Clive Sinclair had the same idea, so the Sinclair Microdrive was born.
        It worked somehow and the contraption was faster than a cassette tape and cheaper than a floppy disk drive.
        The controller and a floppy drive for the QL had the same price as the QL itself.

        Had a Sinclair QL and overall that wasn’t the greatest storage medium.

  3. One correction: 8-track tapes do not have two sides; they are an endless loop of four stereo tracks recorded in parallel. There is a piece of foil in between each section that the player senses to signal that it should shift the playback head to the next pair of stereo tracks. Whomever engineered the 8-track mix had to decide where the breaks would be, That made for some interesting interruptions in the music that I still hear in my head when I listen to those songs on other media.

  4. I had one of these in the early 80’s. Garbage picked it from a college radio station. It worked and I sold it at a garage sale for a couple of USD$. I always assumed they were made for radio stations, not so sure on that now though.

    1. No way any radio station would use 8-track players. They used a RELIABLE 3-track tape cart format that was higher quality and didn’t jam like 8-tracks. No, the reason for a player that would play multiple tapes sequentially was to compete with “record changers”, which were the dominant home audio source. These could accept a stack of up to six or so vinyl LPs and play them uninterrupted.

    2. I started working out of college at SMC (Sono-Mag Corporation in Bloomington, il) assembling cartridge systems for radio stations. The Carousel (rotating drum) and Cara-Stat (held 20 carts each with their own play head) played 30 and 60 second commercials from a predecessor to the 8track.

  5. They probably used licensed long-play easy listening tapes, elevator music. 101 Strings! One wonders how long they lasted being twice as thin as an album length tape.
    It would be easier to use a 12Volt DC to 50Hz inverter to run the motor or the whole thing.
    Nearly everywhere in the world lots of things run on 12Volt DC. Truly universal power except no world standard for a connector, the cigar lighter jack being the worst.

  6. Grew up around them but most folks were transitioning to cassette as preferred sound medium of choice by then. Based on my observations, I think it was the difficulty in dealing with more complicated tape transport and tape design that doomed the 8-track. But having a cassette to 8-track converter was a definite necessity if that old car in the garage only had the latter. Much cheaper than buying a new cassette headend at the time and worked well enough, though having to use the play/fast-forward control on the adapter itself instead of the radio wasn’t the best user experience. Guess whoever did that recent bluetooth cassette “hack” isn’t complaining much about those converters.

  7. I would have had to machine a new motor pulley with the circumference calculated at 6/5 of the existing one…noting the pulley is curved to keep the belt centered.

  8. With 8-track cartridges being endless loops without a capstan, and almost every design having the back of the cartridge ‘hang out’ of the player unencumbered: were there any ‘extended cartridges’ made with a larger tape loop on an outboard platen?

    1. In ’77 I worked at Sono-Mag Corp in Bloomington, IL assembling radio station tape equipment. One item SMC sold was a Time and Advert cartridge machine. The endless loop 8track like cartridge for the time was about the size of an LP record. It would answer the phone, play a quick ad for a local business and then the At The Tone The Time Is xx:xx with the hour coming from one cart and the minutes coming from the other.

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