"mc" wrote in message
...
I have a JVC cassette deck from about 6 years ago that is one of their
top-of-the-line models -- auto reversing, dual deck, and when it records,
it tests the tape by recording a test signal in order to adjust its bias.
Very nice.

Its one flaw is this: It's not willing to apply much torque to the tape.
If it encounters a tape that has minor mechanical problems, it will
flutter badly or auto-stop when a cheaper deck would have just kept it
going.

Being gentle with the tape is probably meant to be a virtue, but I'm
needing to copy a large collection of older tapes in very variable
condition.

Is there likely to be an adjustment inside to increase the amount of
torque that it can apply?

It has always been like this, which is why I don't think it's a worn-out
belt, although it's conceivable that it left the factory with a belt too
large or greasy. I've never opened it up.

Thanks!


Low take up torque has nothing to do with transport speed, so for a start,
we can eliminate that. The transport speed is governed by the contact
pressure between the pinch roller, and how well the tape is made to ' stick
' to the capstan by that pressure. Obviously, the capstan has to be rotating
at the correct and stable speed, but if some tapes play ok, you can pretty
much eliminate that also. Sometimes, excess take up torque can cause
flutter, and sometimes, with some tapes only. This comes about as a result
of the takeup torque overcoming the amount of stick of the tape to the
capstan.

The problem can also be caused by poor freedom of mechanical rotation of the
trailing tape spool. This can be as a result of a dragging reel table or the
table brake not coming fully off, or poor low quality spool mechanics inside
the cassette. This time, the speed variation occurs as a result of the
trailing spool ' tugging ' on the tape, so again the stick between tape and
capstan is reduced, and the tape slips.

If you can run the machine with the deck removed, so that you can get to the
pinch roller arm, you can try pushing some extra tension onto the arm, to
increase the pinch roller / tape / capstan pressure. If this produces a
result, run the deck with no tape in, and see how easy it is to stop the
pinch roller with your finger. If it's very easy, then either the surface of
the pinch roller hasn't got enough friction - they do get ' glazed ' after a
few years service - or there is insufficient spring tension on the arm, or
the arm is being restricted before it is able to apply full spring tension
to the pinch roller. I have seen this occur where there is a mechanical stop
tab, and it is bent slightly out of alignment.

Excess takeup torque problems can be easily identified by stopping the take
up spool briefly, but make sure that there is plenty of space for the tape
to spill out, otherwise it will wrap up around the capstan.

Generally, these faults are fairly easy to identify, but you really do need
to be looking with the deck out, so you can get a good look at the whole
transport path. Good luck.

Arfa