Citizen CS900 8-track player

[dsergeant]

I have a couple of 8 track car players which have come in with some cassettes. One, a Binatone, appears to work but not connected any speakers yet. The other, a Citizen CS900 with instruction manual containing circuit, does not. No movement from the mechanism when a cassette is inserted. Quick tests showed the motor is not turning, it has 12V going to it but not turning and meter checks suggest it is open circuit. Obviously obtaining a replacement motor is unlikely and it is much bigger than most of the cheap cassette motors. The belt also needs replacing though that is for later.

Anybody with experience of these or is it BER?

Thanks
Dave

[Nickthedentist]

Have a look inside the motor, Dave.

There may be a mechanical, centrifugal governor with its contacts tarnished.

Nick.

[dsergeant]

You may be right. But getting inside it Nick may not be easy. Not removed it from the chassis but it seems hermetically sealed.

[Nickthedentist]

You may be right too! But I suspect there may be ways and means which may be feasible for clever chaps like you!

Otherwise, post a pic and maybe someone will come to the rescue with a salvaged replacement motor.

[dsergeant]

Just removed the motor from the deck. Once the outer screening covers were off it was a couple of small screws to remove the plastic tag board and access the inners. Although the slip rings and contact strips don't look brilliant the real fault is that one of the windings has gone open circuit with clear signs of a burn up. So not repairable.

Photo of the motor attached. Diameter 39.2mm,, overall height 38.8mm. Shaft 2.4mm length 10mm. No identification other than S7206A stamped on one of the screening bits which I expect is a date code. 12V DC but no idea what rpm or whether CW or CCW.

Dave

[TonyDuell]

These motors don't normally have many pole (5 or 7 pole armatures are common) and thus are not hard to rewind. It's only 12V (not mains) so the insulation is not that much of a problem either. You need to make careful notes of where the ends of the winding connect to the commutator, how many turns and the thickness of the wire.

I rewound both motors in an HP9125 calculator plotter (OK, a lot harder to find than an 8 track player, so well worth the effort) and they worked second time (I mis-wired the commutator the first time).

[dsergeant]

I had a look into rewinding the coil but decided it would be a lot of work - the wires are wound through holes in the armature so without the proper tools it would be quite tricky. As I said earlier a second 8 track machine was available. With just a belt change that is now working fine. One working, one BER, seems a reasonable deal.
By the way I found if I played the cassette with the deck upside down the tape spooled out of the slot... the internal mechanics of these cassettes clearly doesn't cater for such things. Managed to get the tape back without having to open the cassette, puzzled how it manages to keep it tight inside as nothing turns the inner spool other than the pinchroller/capstan pulling the tape out.

[8 Tracker]

Yes, 8-tracks don't like being played upside-down. Sideways is OK, but invert them and they are not happy. Sometimes, they will even sulk after just being stored upside-down.

The centre spool is turned by the tape being pulled from the middle of the reel by the capstan / pinch roller. The tape returns to the outside of the spool. But because the outside is a larger diameter, it is always trying to pull more tape onto itself than is being supplied. This keeps the tension and is also why the tape has to have a graphite backing. It enables the layers of tape to slip against each other as they move towards the centre. If you ever have a cartridge that has a loop of tape pulled out, they way to get it back in (as long as the cart is running freely) is to pull more tape out. This may seem strange, but it's the way they work.

Mark.

[dsergeant]

Indeed, I couldn't understand when I pulled more tape out the loop became smaller..... clever stuff.