Recently I had the pleasure of assisting a friend rebuild his Ampico,
in return for his expert assistance in rebuilding my computer that was
severely damaged by a lightning strike last fall.

While the glue pot was hot, and the materials were spread out all over
the house (I gave up my workshop long ago when I retired), I thought it
wise to check out my own Ampico "A" expression system, since it seemed
sluggish and the expression was somewhat muddy.  (I had blamed it on
the small piano, and never thought much about the expression
mechanism).

I removed the bass and treble units.  To my horror, I discovered the
1994 restoration had aged beyond my expectations and many leaks and
holes in the pneumatic cloth had occurred.  Here is what happened next:

I checked and tested every square centimeter -- I found leaks everywhere!
Even the wooden valve stems were porous.  Air was seeping through the
stems almost as if they were made of a soda straw,  The square intensity
pneumatics had pin holes in every corner.  The gaskets had compressed
and were also leaking.  The pouches were leaking.  It was a mess!

I carefully removed the valve units, marking each one carefully with
removable label tape, so that it would go exactly back in place.  I
made a cardboard block to hold the screws, as not all are the same
length.  Next, I removed the old cork gasket in preparation for new
ready-made gaskets.  Unfortunately the ready-made gasket holes did not
line up with the holes in the valve block covers and also were too
thick.  They were useless.

I had to make new gaskets from thin cork gasket material.  Not a bad
chore, using an inked stamp pad to mark them and using the block to
transfer the ink to the cork.  I used an X-acto knife to cut the holes
after the cork had been glued to the block covers.  The trick is to
keep everything immaculately clean, and no crumbs or dirt into the
works.

While the valve covers and screws were removed, I found that a drop or
two of Super Glue down inside the nearly stripped and dry rotted screw
holes is a dandy way to tighten them up.  (Be sure to let the glue dry
8 hours or so or you could end up with screws permanently glued in
place.)

The porous valve stems were dipped in thin Phenoseal, allowed to dry
and received a coating of pure talc to prevent any sticky residue.
There were leaks in the end grain of the wooden valve blocks, and also
leaks where they were drilled an plugged during manufacture.

All valve leather was replaced top and bottom of each valve.  Again the
ready-made valve leather was inferior, and home made ones were not
difficult to make from a better grade of leather.  While the valves
were out, I tested the edges of the valve seats and found they also had
leakage where they had been pressed into the wood.  These I sealed with
a very fine ring of Phenoseal, making sure that no Phenoseal got on to
the valve seat itself.  The valves were then correctly gapped, and the
top glued in place.

I removed and recovered the three intensity pneumatics using a block
spacer that I made to achieve the correct span of the pneumatic cloth.
I found additional failure where the pneumatic cloth was overlapped
and originally glued with hot glue.  Therefore I chose to glue the
pneumatic cloth to the wood using hot glue, but glued the overlap using
plastic glue.

Yes, I am aware that synthetics are to be avoided, but an overlap with
hot glue is risky.  I also have found that synthetic plastic glue is
good for overlapping hinge ends of some pneumatics.  The plastic glue
is not applied to the wood, only the pneumatic cloth-to-cloth bond.  It
really makes a better job and will not loosen or buckle like a hot glue
overlap can sometimes do, especially if the first hot glue layer is not
allowed to dry sufficiently before the second one is applied.  (Years
down the road, when it requires replacement, the overlap will be
discarded complete with synthetic glue, so why all the fuss?)

Carefully mark both top and bottom of these square pneumatic boards.
While they look identical, they are not.  They must be replaced exactly
as they were placed.  The screw holes must go back exactly as they were
removed or they will not fit properly.  There are four screws under
each square pneumatic which hold them to the board.  It is important to
ease the holes in this board using a small drill to prevent them from
binding when the screws are replaced into the pneumatics.

Rather than using cork for a gasket under these three pneumatics,
I used leather (the cork being too thick to grasp the screws when put
back in place).  Keep testing, using every method available to test]
for leaks.  Test as you proceed.

Once the three pneumatics were glued in place, I placed a hose on the
hole of the board (under where the valve block is secured) that leads
to the pneumatic, and draw on it to test for leaks.  Note that the four
screws on the top of the square pneumatics are a source of leakage too.
Don't trust anything not to leak -- Test it!

Needless to say, I also replaced the pouches and rubberized them using
one or two coats of very thin Elmer's rubber cement, thinning it with
Coleman lantern fuel (naphtha, being careful as it is very flammable).
Each pouch was dusted with talc (not talcum powder) and replaced.
I have not had any problems with Elmer's rubber cement in regard to
stiffening of the leather.  In fact, the jar is the same one I bought
in 1994, and nothing I have used it on has become damaged from it.
When it becomes too thick, I add more naphtha.

The cancel pouches that are under the motor cloth cover are quite
difficult to reach and replace but once the old material is removed one
can see that they are installed in reverse.  The valve button being
placed on the pouch before it is dished and glued in place.  These are
rubberized from the bottom side of the leather, again using talc to
prevent any sticky residue.

It is time consuming work, and one must be meticulously clean while
working and use the vacuum liberally to prevent any specks of dirt from
lodging into the mechanism, before it is assembled.

When replacing the rubberized cloth cover on the bottom of the board,
cover the pouches with a circle cut out of paper to prevent any hot
glue from getting on the pouches.

Once the job was complete everything was tested again for leaks.  All
was well and placed back into the piano and connected.  The difference
was amazing!  I now hear things recorded into the rolls that I have not
heard in many years.  I am enjoying my Ampico more than ever!

Bruce Clark