National Multiplex data cassette tape drive

From: William Maddox <>
Date: Mon Aug 30 00:05:27 2004

Bill Dawson wrote:
>>Years ago, I owned a data cassette drive made by a
>>company called National Multiplex, presumably long
>>defunct. It was obviously a modified audio cassette
>>recorder, but in which the internal electronics had
>>been completely replaced. Unlike the prevailing
>>standard for cassette-based data storage on micros
>>in that day, this drive used saturation recording
>>(NRZI, I believe) instead of a modulated audio carrier.
>>It was a very functional replacement for a paper tape
>>reader/punch, and ran up to 9600 bps using hi-fi grade
>>audio tapes.
>>I would be interested in locating one of these beasts
>>to replicate the setup I had on my IMSAI before I sold
>>the drive years ago. The drive came with schematics,
>>and as far as I remember, the circuitry was rather
>>simple -- a couple of op amps and a few gates.
>>Alternately, if I can locate a copy of the drawings,
>>I may attempt to reproduce the design using a
>>contemporary audio cassette mechanism.
>>Has anyone ever seen one of these?
> Yes, I still have the one I used with my SWTPC 6800,
> along with the supplied documentation. The unit is
> just a modified portable cassette player. National
> Multiplex gutted the usual cassette player-recorder
> circuitry and installed their circuit board. They also
> increased the tape drive speed (by changing the diameter
> of the drive motor pulley, IIRC). There were several
> models, but they were all called Computer Aid. The square
> black plastic model CCA-7 was the most popular and are
> the ones I have. This model has the level meter on it.
> I found and purchased another on eBay several years
> ago, so they're still out there. Another model is the
> rectangular silver Computer Aid model DC-3. If I come
> across my documentation for it (I have a good idea where
> it is, I just don't have the time to look for it), I'll
> scan it and send you the url. It'll be on
> somewhere.
> Bill
Received on Mon Aug 30 2004 - 00:05:27 BST

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