Hello Martin,  In the early 1980's my Universal began losing one note
after another as the Perflex pouches became weak and failed.  I found
this to be a very simple stack to work on.  The pouches are simply
short PVC rings with pouch material glued to one end.  I chose to
replace the Perflex with tan pouch leather and they performed fine
through the mid-90's when I sold the piano.  The rebuilt pouch
assemblies are simply press-fitted back into the valve chamber, which
is machined from an aluminum bar.

The early stacks used wood pneumatic fingers which would be simple to
duplicate as Robbie suggests.  The finger that is glued to the stack
has a short stub of PVC tubing through it that serves to locate the
finger on the stack and to keep adhesive from entering the air passage.
Later Universals had plastic fingers.  The valves are small Neoprene
type buttons attached to a short fluted stick.

Valve clearance is determined by the thickness of a vinyl gasket that
runs the length of the stack and separates the upper and lower valve
chamber.  This is a very simple stack to work on and is easily removed
and opened up for inspection.

When Universal stopped production I believe a company in the east
continued building them under the name Classic Pianos.  If they are
still in business it may be possible to purchase many of the parts
for the overhaul.

Hopefully another reader will suggest a parts supplier for the
Universal brand.  Good luck.

Mike Campbell
Kentucky

 [ The Universal piano tooling was acquired by Classic Pianos which
 [ later became QRS Story & Clark Pianos in Seneca, PA.  -- Robbie