Regarding Ampicos that won't play immediately, that is usually
caused by an upside-down block valve whose travel is too great.
If the player is of the Amphion-action type, then the chances are,
that valve is in the stack.

Remove its cover and listen for the valve.  You can make it do this
anytime you want by raising stack pressure, on whichever side you
are able to listen for it first.  Put the piano modulator switch on
Brilliant, air motor to stall, trackerbar covered, and pull 1T and
1B respectively.  This raises crescendo pressure and the valve will
get sucked in.  You will first locate it by its sound, and then
unclamp it and fix it.

In case it's the stack cut-out valve and that circuit, then you may
have another problem, but that's an outside valve (primary).

Craig Brougher