The "jack box", or reversible stack, for an Aeolian pipe organ is
the pneumatic device which converts an electrical pulse generated by
a hole in the roll to a continuous electrical signal which turns on a
particular rank of pipes, and which cancels this signal when another
short pulse, generated by the same hole, is given. It is very clever,
and more information about it can no doubt be found in several well
known web sites.
The purpose of this piece is just to relate that, not being sure about
the intended pressure this unit was supposed to work on, and having
been given information that suggested 18 inches water gage pressure,
I used the blowing outlet from an old vacuum cleaner. This would have
given at least 18".
Two days ago, during a visit by an enthusiast, the old vacuum cleaner
stopped working, and no more Duo-Art rolls could be played. These mini
"disasters" often have a good out-come, and for me this was certainly
the case. Rather than try to repair the 1960s Electrolux, which had
given up the ghost, I tried the jack box on the available wind in my
relay room, of 4 inches w.g. Worth a try I thought, and as expected,
most of the jacks refused to work, but quite a few _did_ work.
If some would work at 4", then they all should, so I took off the glass
covers and inspected the jacks which did not work, or were sluggish.
How delightful it was to find that they were the ones that were very
stiff. If anyone wants details of how this stiffness was overcome,
I will write back.
Suffice it to say, the problem was not difficult to solve, a little
electrical spray lubricant finished the job, and now even during the
"explosive" swell shade movements of Edwin Lemare, the jacks fly up
and do their job perfectly. The old vacuum cleaner was unsightly,
noisy, potentially dangerous, required additional switch gear, and
consumed more electricity. Its removal was a great joy.