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MMD > Archives > November 2020 > 2020.11.26 > 05Prev  Next

Pianola Repeats Chained Note Perforations
By John Grant

Joel, you will no doubt receive several responses on this, but
I'm going to come down on the side of bleed(s) that are too large,
pouches that are too porous, or a combination of both, so that any
slight occlusion of the tracker bar hole -- due to a narrow paper slot
compounded by the paper bridge -- would allow the combined/enhanced
exhausting power to begin, even complete a re-seating of the poppet.

If I am correct, the following diagnostic should be definitive: Speed
_up_ the Tempo at least 10 points or more; the issue should lessen or
become less frequent as the bleed/pouch exhausting has less time to
reset the poppet. Conversely, slowing _down_ the Tempo should aggravate
the issue, causing more valves to exhibit the problem if they currently
are not.

Are _all_ or _most_ valves exhibiting the problem now? Are they more
centrally located in the keyboard where the tubing lengths are shorter
and more quickly exhausted?

Even if the serviceable or original pouches were not sealed, I would
do so. Saying "they are] no more porous than the new .070-.080 [sic]
pouch leather I could have replaced them with" is not exactly a useful
comparison, as "new" pouch leather is notoriously leaky. (I believe you
meant 0.007-0.008 [inches]).

It would also be useful to know the size of the bleeds, if they are
uniform and display no obvious signs of having been enlarged or

John Grant

(Message sent Wed 25 Nov 2020, 21:54:12 GMT, from time zone GMT-0800.)

Key Words in Subject:  Chained, Note, Perforations, Pianola, Repeats

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