>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 18 May 2005 09:54
>To: piclist@mit.edu
>Subject: [EE]: Microcassette mechanism interfacing
>
>
>Hi,
>  I've just salvaged a microcassette mechanism out of an old 
>answering machine. Reverse engineering the motor segment was 
>easy enough - run the motor in reverse and the mechanism 
>switches into a fast-rewind mode, run it the other way and the 
>mechanism switches into record/playback mode.
>
>  I've also identified what appears to be an optoreflector on 
>the controller board. It's situated under one of the tape 
>drive pulleys, and has three leads. Two appear to be the LED 
>anode and cathode, the third seems to be an output of some 
>description. The sensor is SMD, in a clear case. I suspect all 
>I need to do is feed it 20mA across the LED, then take the 
>signal from the output pin, but I'm not sure if the output is 
>open-emitter, open-collector or totem-pole (I suspect it'll be o/c).
>
>  The big problem is interfacing the magnetic head to 
>something. I don't have the foggiest clue what I need to do to 
>record on the tape. I know there's supposed to be an AC bias 
>signal fed to the record head and the erase head, but I can't 
>find any concrete info on how to determine the frequency and 
>amplitude of that signal. The same applies to playback 
>circuitry - no info on output levels or required amplification.
>
>  Does anyone have any schematics lying around that I could 
>get copies of? Most of the stuff I've seen consists of one 
>chip, the heads and a few passives. Something that's based on 
>common ICs (standard opamps, transistors and passives) would be great.

Simple preamp design at
http://www.elektroindonesia.com/elektro/el0101a.html

Can't help with the recording side.  This is the kind of thing there
used to be hundreds of DIY designs for in the popular electonic/hi-fi
magazines many years ago but with tape well out of favour there is
little interest these days.

I guessing you aren't after "hi-fi" results from this? 

Mike

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