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MMD > Archives > October 1997 > 1997.10.20 > 11Prev  Next


Ampico B Pump Pressure
By Craig Brougher

The pump pressure in Ampico B's does vary.  I've done about a dozen of
them, I think, and have noticed a different number of coils in each pump
regulator spring, as well as slightly different diameter wire in two of
them.  I have also discovered that the coils were often pulled out, being
over-stretched so often by the amplifier.  The best springs were always
the heavier gauge with more coils, so I copied the best one and now sell
that spring, postpaid, for $9, if anybody wants one.  They really improve
the system.

Randy's problem of not being able to get the proper pump pressure is
possibly attributed to this spring, but it could also be a valve that is
riding up, or a valve seat not glued tightly down.  When the piano
pressure rises, that valve would then seat tightly, giving him a great
top end, but up until then, it would cause a lower than normal pump
pressure.

In regard to the really good answer that Bob Taylor gave Randy in regard
to the extra nipple in the control block, I remember having seen that
modification too, and forgot about it.  My own instrument is the older
design in the book.  I think, however, that a 15" pedal pressure is too
low for perfect tracking of a roll when the trackerbar pressure goes up
to maximum.  I tried that pressure and decided it wasn't sufficient, so
I cranked it up to about 18-1/2".  I guess it's all according to how you
like to set them up, but it does make for a 20% faster pedal and likewise
a stronger tracker.

I have a hunch that the reason I have never had a problem with either the
tracker or the reroll/repeat, the variable play brake, or anything else,
even with the old tubing system, is because I have always adjusted my
pedal pressure up a little higher than 17".

( One other thing that just occurred to me about these differences in
pressure mentioned is the fact that the usual Marshalltown vacuum gauge
varies greatly in readings.  I have hooked up about ten of them together
on the same line and have read differences of 5-6 inches of vacuum.  Not
only that, but the same gauge's repeatability varies about 2", sometimes.
These do not seem to be very good gauges, and I stopped using them years
ago.  I now use three precision Swiss-made Haenni gauges -- which, as I
understand, are now made in Germany -- and paid less than I would have
for a Marshalltown gauge.  They have an adjustable zero, and are very
repeatable.  There are also other very good low vacuum gauges. )

I have always been curious, though, as to where Bob Taylor has found those
figures.  That old information seems to be always surfacing and I learn
something new every day.  I just love it.

Craig Brougher


(Message sent Mon 20 Oct 1997, 14:37:18 GMT, from time zone GMT.)

Key Words in Subject:  Ampico, B, Pressure, Pump

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