I am writing to ask for constructive advice regarding the Welte
(Licensee) player action.  This particular type of player is
relatively rare here in the UK, although I believe somewhat more
common in the USA and perhaps elsewhere.  Hence there are few
player-owners in this country to whom I can turn for first-hand
practical knowledge and advice of this system, and I am hoping that
there will be MMDers, perhaps in the USA, who will be able to comment
from their own first-hand knowledge and practical experience.

My Welte (Licensee) action is the upright version, housed in a
relatively modest Waddington piano.  It was overhauled by a previous
owner and has been playing reasonably well until recently when, after
finishing and re-winding a roll, it then simply refused to play.

Testing the pump shows some 30" of vacuum being produced, which
seems adequate to me.  "Play" and "Re-roll" both work perfectly from
a mechanical viewpoint and all is well with the wind motor and its
governor.  However, none of the notes respond at all as the roll
unwinds and testing shows the entire expression mechanism plus the
stack itself to be bereft of vacuum, although the two modulator
pneumatics (supplied directly from the gate box) respond when actuated
by allowing air into their control line.

The failure has the characteristics of a faulty main action cut-off
valve but, having pored over the official technical service manual and
its associated tubing diagram, I cannot seem to find evidence of the
existence of such a valve (though there must surely be one).

I would appreciate advice from anyone who can confirm the existence of
a cut-off valve in the Licensee action and its precise location -- or,
alternatively, any other practical advice on what may be the fault and
how I might best approach its rectification.

With thanks in advance, and with apologies for what I am sure will be
seen by many as a naive enquiry.

David Perry, UK