Hello MMD.  I removed the upper action from my Steck half Duo-Art
a few days ago and have spent a good deal of time since prowling
nervously around it, identifying the various vacuum lines, and
generally working out what is what before unscrewing anything.

When Andy Hood's query appeared in MMD, I dug out my half Duo-Art
tubing diagram drawn some years ago by Arthur Jones of the British
Player Piano Group.  I obtained my copy about three years ago from
the PPG; probably it is still available.  However the tracking system
in my Steck is not the same as in the above-mentioned diagram; it is
the type 4 mentioned in Jeffrey Wood's MMD posting of 071011.

There is also a diagram of this variant of the system on page 161
of Ord-Hume's book, "Player Piano".  In some ways his diagram is
a little clearer than the one in the Duo-Art manual, _but:_ there
is a mistake in the text at the bottom of the diagram.  It states:

 "On re-roll, suction is applied under the pouches so that the
  auto tracking system is rendered inoperative."

In fact, suction is applied only during play mode.  During Fast Forward
and Re-roll, the undersides of the pouches are open to the atmosphere.
I discovered this about 35 years ago, when I was working on my first
player.  I wrote to Mr. Ord-Hume about it at the time, but he hasn't
yet replied.

My experience is that once this system is set up properly, it doesn't
need touching for years.

John Phillips in Hobart, Tasmania