Newbie so Hello !!!

[rottie]

Right then, I have bit the bullet and decided to finally try and build what for me is an ambitious build of a small project, and figured having used forums for classic car advice, dog training advice etc etc you get the drift, you guys came up as the first hit on google for "Electronics Forum"
My name is Nick, im a 39 yr old nutter with a taste for oddball vehicles and trying to make things that you cant buy myself as thats more fun isnt it !! This brings us to my current undertaking, now bear with me , some of you are too young to probably even remember this sort of thing but im doing up a classic car and the stereo side of it needs to be "In keeping" yet modern to use.
My weapon of choice is this.

For those who are wondering it is called an 8-track player, it played a cartridge of continual tape (wound out from the middle and back in on the outside edge) and contained 8 tracks of audio giving 4 sets of stereo recordings, changing channels was done by the tape joint being metal and it bridging contacts making a soleniod jump the head up a small increment to the next set of stereo tracks, all clever stuff in the day, playback was by what appears to be a standard type stereo head in the back of the unit.
This is a cartridge

It has no holes on it at all for any sort of spool, the tape was moved literally by the pinch roller that was in front of the read head.
This is the cartidge in the unit, showing there is space for what I have planned

So what do I have planned.. no laughing please and yes I know I can buy a head unit that plays mp3's, I have my reasons for trying to do this, partly to prove that I can
I want to build an MP3 player into this cartridge, I am hoping by using another playback head that I can mimic those cassette adapter things you get that go into a cassette deck to plug an mp3 player/cd player into them. I also want the unit to have a USB port (seen those on maplins) and an inbuilt battery, I know the contacts that would normally be bridged to change the track are 12vdc but wether or not I can draw off those for charging without it trying to continually change tracks I dont know. I want to have control buttons across the back edge of the cartridge, and if I can find a small enough "donor" mp3 player an LCD screen in the part of the cartridge that still sticks out, so there you go, am I mad or is it a good idea? the fabrication side of it is easy, its the electronics and control circuitry for the charging that im not sure about.
Thanks for reading

 

[rottie]

Forgot I hadnt put photos of the business end so here they are,
the main end of the cartridge, showing from left to right
Slot where pinch roller used to be
Slot where the playback head will go (I will need a means to trim this up and down, was thinking a screw thread and a knob on the back of the cartidge)
and the part where the track change contacts sit

here is the view into the neck of the player with the flap open

you can see the track change contacts to the left (above yellow wire) these are literally bridged by a metal strip on the tape itself, then there is the playback head, and finally the pinch roller that drives the whole thing, the little wheel to the right is what simply locks the cartridge into the player

 

[(*steve*)]

In theory, you could get one of those MP3 players which fit into a cassette and use the innards.

In practice, there is one very important difference between cassettes and cartridges that you may need to carefully consider. That difference is that the cassette is a 2 track device, the cartridge is 8 track.

I suspect the spacing between the tracks is going to be different, but also the head of the cartridge moves up and down to access the four pairs of tracks.

I have no idea if the "head" used inside a cassette MP3 adapter uses a head similar to the playback (or perhaps the record) head of the player, but it certainly has the same spacing.

You may need to get a head from a dead cartridge player so that the heads physically match.

You also may have to deal with the face that your player only works for a single track.

 

[KrisBlueNZ]

Just a random thought here... Could you just mount a memory card (e.g. an SD card) in the cartridge with its pins accessible to make contact with a connector in the player, and put all the MP3 playing stuff in the player? You would just put the music tracks on the SD card as MP3 or WAV files.

 

[rottie]

yes your right on the track spacing, the tracks are 1-8 but are played 1-5, 2-6, 3-7, 4-8 to give the 4 stereo outputs, so will take some tom foolery finding a suitable head to "talk" to the original head, I have 8-track players here but I loathe cannibalising them for spares as they arent the easiest things to come by these days,

Steve I was indeed hoping to use an existing mp3 player for the playback part of my project, and am looking for one with a 20mm width screen as I have 23mm of cartidge visible out the player when its inserted, memory wise I would think 4 gig would be adequate as to be honest I like to chop and change what I have on the player, tried the big player route with everything on and I got lost on it.

Kris, I wasnt the cartidge to be universal as I have 3 or 4 players in various vehicles and at home, great idea though.. the worlds BIGGEST SD card lol

I mocked this up last night using Googlesketchup and hopefully it will give some idea of what im trying to do, ignore the screen size I had had lots of guinness and hadnt measured how much space I had for the screen

 

[KrisBlueNZ]

I have 8-track players here but I loathe cannibalising them for spares as they arent the easiest things to come by these days,

You could try eBay, obviously.

Kris, I wasnt the cartidge to be universal as I have 3 or 4 players in various vehicles and at home, great idea though.. the worlds BIGGEST SD card lol

LOL I understand. I was assuming you would have more cartridges than players, so it would make sense to have the MP3 player built into the deck rather than the cartridge.

Doing it the way I suggested would give better sound quality and make it easier to add more cartridges in the future. It would also mean you wouldn't need batteries inside the cartridge, although you could avoid that by adding contacts to the cartridge so the player could provide the power.

It would mean that you couldn't display the current track information on the cartridge itself though, unless you had another set of contacts for the interface to the display.