Hi All,  Nevin Engle writes in 130610 MMDigest:

> When I apply 10 inches of water vacuum and start uncovering the
> tracker, the vacuum gradually lessens when about half of the holes are
> open.  Any ideas what is going on and suggestions for improvement?

It sounds to me like you did a decent job rebuilding the stack.  As
each of the holes in the trackerbar are opened, a small amount of
atmosphere is constantly entering the stack via the bleed holes,
which will reduce the vacuum level by a small amount.

Naturally, there are other components that come into play, namely,
the exhaust valve facings, the striker pneumatics, and any gaskets
that might be between the vacuum chamber and the strikers.  However,
assuming they are all relatively air-tight, I'd say that what you
are experiencing is completely normal.

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA