According to the internet a respected deck in its day.
Had to deal with the slip clutch buried in the mechanism. Photoed before
disassembly just in case. Reassembled and the 2 pinch wheels were fighting
one another. A strange pair of springs one acting against the other for the
"reverse" pinch wheel assembly. I must have put one of these springs back
with wrong anchor position. Correcting that and its playing and FF and REW
ok.
These units are called 4 head, 4 pairs of screened stereo wires going to the
head but all seem to relate half the tape. So one question is why 2 pinch
wheels when there seems to be no proper "reverse" side play or loop control
function as a fixed head.
Repeat sends back to replay the same side.
The "reverse" pinchwheel seems to operate only just clear of the reverse
capstan spindle and has a strange guide that protrudes around the pinchwheel
and into the recess of the cassette - what is the function of that
protrusion and a non pinching pinch wheel ?
What do the 4 stereo heads do ?

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Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/