If I'm not getting the Dynavoice mixed up with another keytop player,
I believe that its origins were in Kansas City area in the 60's when
one of the owners of Gribble Music Co. had an idea.
At that time, Midwest Research Institute (MRI) was looking around for
a local design project they could help some entrepreneur with, and this
idea of a keytop player intrigued them. So they settled on the keytop
player as their Good Samaritan project. (I realize that there was also
another brand of plastic keytop player using a different design alto-
gether, so I may be getting the names confused, but I am reasonably
sure that Dynavoice is the one).
Some of the units had self-destructing valve units made of plastic with
rubber pouches. The valve bodies were of a type plastic that disinte-
grated with time and the molded integrated plastic pouch nipples would
break off, incapacitating them. They looked like you could replace the
nipples with brass ones, however. The design was compact because the
striker pneumatics were accordion molded tubular rubber and, at least
in the one I looked at in the early 80's, still in very good shape.
The basic problem I saw with the unit was a design flaw created by the
high vacuum pressures required due to the tiny striker bellows. That
is, the vacuum pressure had to be very high in order for the unit to
work. That made the vacuum motor awfully loud, which is the main
reason the unit never sold very well. But it also created a system
that wouldn't track rolls either, because although it had a pretty cute
little air tracking system that should have worked well, the vacuum
clamp on the paper going across the trackerbar was so strong all the
time that sideways paper motion was all but impossible.
They had a transposing trackerbar which could be used as a "roll-
chaser" manual tracker if you wished. The original tracker bars were
always very roughly surfaced too, creating a lot of resistance to the
paper. I would think that once the Dynavoice was playing again, if the
trackerbar was laboriously polished up, it would at least stand a
chance of tracking rolls to a degree.
[ There was a surface treatment process, possibly called "Microfine",
[ which coated the metal surface with a layer of tiny glass beads.
[ We used this on the magnetic tape guides in several products made
[ by Lockheed many years ago. Another potential coating material is
[ Teflon. -- Robbie