Robert Nicol is inquiring how to identify the stack cut out in the
pump distributor block for an Ampico A grand. For a grand pump that
is in place, one side of the pump will have a rectangular block that
has one large tube that come out of each end of the block. This is
the distribution block.
If you feel on the top of this block there should be two fairly large
nipples, which should go to a reservoir. In between these two nipples
on the top of the distribution block, there should also be one nipple
of control tubing size (slightly larger than tracker bar tubing). On
the interior of the distribution block, the other end of that nipple
goes to the stack cut-out pouch. It has a set amount of travel and
should be air-tight.
If you can detach the tube to this nipple from its other end you
should be able to suck and blow on the tube and get resistance in both
directions. If you don't get said resistance in both directions, then
the pouch is either damaged and is leaking, or the tube that goes from
the nipple to the pouch is damaged and needs to be replaced.
Now, if there is resistance in both directions, then the next possible
culprit could be the cut-out block from which the original tube was
removed. That is a small black valve block that is usually screwed in
place to some wooden part of the piano frame. That should have three
nipples coming out of it. One nipple goes to the cut-out block, one
goes to the vacuum supply and the third should go to the drawer.
Hope that helps out.
Good luck, Mike Walter