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kinchmusic@... wrote:
Higuys.I'vebeen onto Martin, discussing whether I should replace the pinch rollerson my machine. They are original and most definitely showing signs of wear.He says he can regrind them angling the edges so making better tape contact.However, I have the feeling that as they have become worn, it has affectedthe tuning of one note with another. Surely if you have pinch rollers thatare a slightly different diameter from each other, they will be out oftune with each other to an extent. So I'm inclined to go for a completenew set.Anyoneelse have any opinions on the science of all this?Cheers. Andy K , EMI m400 #E4/140SGreetings All ,
To-date, I have resurfaced,reconditioned and chamfered
pinchrollers on 10 Trons . No change in note-to-notepitch
should be expected whatsoever.Here's the theory behind it. The capstan diameter and its
rotational velocity is the sole determining factor for trans-keyboard
stability of pitch.
The pinchrollers are simply "idlers", following the capstan's
movement to bring tapes into motion.
In principle , if their diameters were smaller, each roller would
turn more quickly relative to capstan dia. & speed. Reverse istrue
if the pinchroller were of larger diameter...it would turn slower.
But each tape regardless is moving at 7.5 IPS .However, if the resurfaced roller has a flat spot, that would
induce pitch variations for that particular note. The dreaded
"wobblies" is related to pinchroller rotation problems, but more
associated with wear of the shaft and nylon bushing within.
And of course, alignment squareness to overall tape path .For example, I cleaned/resurfaced all 70 pinchrollers in MK-I
#124. Though 40 years old, None needed replacement.
They had a "glazed" look to the rubber surface which
straightaway was removed with abrasive pad and treated
with reconditioning fluid.Feel free to respond with your ideas on this very good point
of Andy's. Have a wonderful weekend ....Cheers, JK