-- Bypassing the control & checking for other problems --

I agree with Eliyahu Shahar in regard to the automatic cut-out block
having filters (fine wire screens) to protect the mechanism.  The
problem is this: Over many years, the filter screens eventually clog,
and they are difficult to clean because when vacuum is applied to the
tracker bar for cleaning purposes, the leather pouches inside the
blocks seals the pathway to the expression mechanism, and prevents
dust removal from the screens and expression mechanisms.

The only way to clear the screens of dust is to disassemble the
automatic cut-out block and/or remove the hoses and use compressed air
in an attempt to clear dust from the screens.  This involves removing
the screws and gasket from the back of the automatic cut-out block,
cleaning and reassembling it.  If the pouch leather is old, the
compressed air may damage them.

Without the screens and pouches, the tracker bar cleaner, when used,
has a clear pathway and is able to remove dust from the expression
mechanisms, as well as other components in the system.

I have fabricated at tracker bar cleaner by using the rubber tip for
a mechanical tracker bar cleaner and fitted it to the hose to a very
powerful vacuum cleaner.  Clean your tracker bar frequently!

If you continue using the automatic cut-out block, be sure to check
the small pneumatic finger on the side of it.  When closed, it must
seal the two projecting nipples for 7-T and 7-B.  Often there is
leakage in either the pneumatic itself, or the pad that seals them.
If one is playing Ampico rolls exclusively, I see no use for the
Automatic Expression cut-out block, other than originality.  If you
bypass it, simply leave it there for purists to use in the future.

One problem area that is often overlooked is the expression and control
hose connections at each end of the stack (upright Ampico pianos) and
drawer hoses on grands, too.  Sometimes one or more of the hoses may
become detached, causing something to be on or off that will cause a
problem.

In addition, the rotary "Modify" switches should be checked for
leakage.  Many were made of pot metal and over the years they tend to
crack and become deformed.  When this occurs there is leakage.

In my own Ampico, I noticed there was very little expression in the
treble section, however the bass was expressing properly.  Upon
checking, I discovered the hose to the treble Subdued valve had become
dislodged causing, the treble Subdued pneumatic to be on, continuously,
but the bass was not.

Again, I stress the importance of checking for leaks.  I have seen many
cases where people have tightened the unit valves so tightly they have
pulled the screw rods out of the stack.  That excess tightness can
damage the unit valves, by distorting them and causing the glued wood
laminations to crack especially along the sides.

Check them!  If the cracks are small, they can be filled in with thick
shellac.  If they are badly warped, I would suspect the valve seats to
be warped also.   The only remedy for this is to completely rebuild the
valves.

Use caution in selecting gasket material.  Some material is a mixture
of cork and rubber.  In some cases, the rubber mixed with the cork has
become hard, making the seal less effective.  I use plain cork gasket
material as used in the originals.

Bruce Clark