04-03-2015, 05:28 PM
That's a puzzler 
I spent my childhood taking apart 1970s stuff - in the name of science, you understand! - and I'm sure that my guilty conscience is what got me into the restoration/collecting scene...
What would help - if possible - would be a picture of the top of the deck. As it is, I can't quite visualise where the cassette is, and what exactly does what...
Perhaps an obvious thing to say, but when in FF, the pinch roller should be lifted from the capstan, and the spool is the only thing that is driven. So it shouldn't be possible for the capstan/pinch roller to throw a loop. Perhaps this deck is an exception to that rule? Yes, simply speeding up the motor in FF (and muting the audio) is feasible, but I can't think of many instances where that is done. I've seen a couple where the speed control is bypassed to get a bit more RPM from the motor, but this is normally in conjunction with a gearing/pulley change to provide the bulk of the speed increase. Does this make sense?
Another possibility is perhaps the spool is being turned the wrong way in FF. Often, a different idler is used (different compared to PB). Don't ask me why, but I can't help feeling suspicious of the belt path (the long one). It's obviously OK at the top-right, where it goes around the flywheel, out to the white pulley and back to the motor. But as it goes around the black pulley, I wonder if it should go the other side, so that the pulley turns in the opposite direction to the flywheel?
Cheers,
Mark
I spent my childhood taking apart 1970s stuff - in the name of science, you understand! - and I'm sure that my guilty conscience is what got me into the restoration/collecting scene...
What would help - if possible - would be a picture of the top of the deck. As it is, I can't quite visualise where the cassette is, and what exactly does what...
Perhaps an obvious thing to say, but when in FF, the pinch roller should be lifted from the capstan, and the spool is the only thing that is driven. So it shouldn't be possible for the capstan/pinch roller to throw a loop. Perhaps this deck is an exception to that rule? Yes, simply speeding up the motor in FF (and muting the audio) is feasible, but I can't think of many instances where that is done. I've seen a couple where the speed control is bypassed to get a bit more RPM from the motor, but this is normally in conjunction with a gearing/pulley change to provide the bulk of the speed increase. Does this make sense?
Another possibility is perhaps the spool is being turned the wrong way in FF. Often, a different idler is used (different compared to PB). Don't ask me why, but I can't help feeling suspicious of the belt path (the long one). It's obviously OK at the top-right, where it goes around the flywheel, out to the white pulley and back to the motor. But as it goes around the black pulley, I wonder if it should go the other side, so that the pulley turns in the opposite direction to the flywheel?
Cheers,
Mark
