Checking the play speed of a cassette recorder.
Requirements: a 1KHz test tape or a recording of an accurate
1KHz tone made on a known good tape unit and played back on that machine
to check, and an audio signal generator
with a fully floating output ie no dc reference if not then de-couple the
output
with a couple of capacitors.Parallel together one channel of the phones
output of the tape and the output of the sig.gen. and a set of headphones
in mono (L and R connected).With approximately equal sound levels
you should get unmistakeable beat note .Reduce the beat to a minimum by
changing the speed regulation of the cassette unit motor.
Diverse Devices, Southampton, England
other electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/