Robbie Rhodes wrote:

> Electrical supplies catalogs commonly list several different
> available coil voltages for a magnet or solenoid.  There's no
> difference in the performance (force & speed) of the high-voltage
> vs. the low-voltage devices when they're controlled by equivalent
> circuitry.

Not true.  Not when used in this application.  Minute differences of
response are quite evident when applied to the travel of a piano hammer.
For almost any other type of use this small amount of change would not be
a factor. They will use the same amount of power to perform the same
amount of work but the true fact is that higher voltage will build up
magnetic flux faster than lower voltage both because of the higher
electrical pressure, i.e., electromotive force, as well as the less
amount of current required to create the same gauss.

> I believe that most of the Mills instruments used a "relay-style"
> actuator which has a stationary core, versus the solenoid with a
> moving core.  Could our Mills experts please confirm this?

The earlier Mills Novelty Co. magnets used a side-moving armature hinged
at the lower end of the solenoid, so there is substantial mass to be
moved.  Later they changed the style of magnet, and used a short armature
type that hinged at the upper end, as mounted, and significantly reduced
the mass and improved the performance.

Mills did experiment with lower voltages at one point in their develop-
ment, as they were concerned about the safety factor, according to
information that was given to me years ago.  I believe that they were
working with 15 VDC. and at another time with 36 VDC.  This was
thirty some years ago and I might be off slightly on those voltages but I
think they are correct.  Anyway, there decision was based on experiments
in the factory that showed the higher voltage produced more satisfactory
results due to its "crisper" action as I was told.

> As anyone with an old 1960s transistor-electronic organ knows,
> it's difficult to keep low-voltage switch contacts clean when they're
> exposed to the oils in the open air.  The Mills electric instruments
> use the hole in the paper to allow a small wire "brush" to touch the
> brass tracker bar, which closes the circuit to the magnet.

Not true,  the Mills instruments do not use a tracker bar in the usual
sense and in no case is it brass.  It is in fact a serrated steel roller.
The contact roller is turned by friction from the roll, and as it rotates
it operates a ball-weight governor at the left end of the roll feeder, as
viewed from the front of the instrument.  As it is in constant motion
while playing there is no problem of dirty contacts.  The contact wires
that read the roll would possibly be less damaging to the paper roll if
operated at lower voltage, as the high voltage of approximately 110 to
120 volts DC tends to cause micro-arcing and to produce sharp points at
the end of the contact wires that then have the effect of acting like
slitting knives on the paper.

The addition of a spark suppression network can materially reduce
possible damage to the roll and a suitable network across the governor
contacts can do a lot toward reducing or eliminating Radio Frequency
noise that is generated by the almost constant arcing while the machines
are being played.  Having owned six Violanos and on Magnetic Piano I am
fairly familiar with these machines.  I have also serviced approximately
another twenty five Violanos around the Mid-west over the past thirty
plus years.  Although I haven't had a Violano for the last three years I
still have a few dozen rolls so if you're interested, we could talk.

> I believe that they discovered that the standard low-voltage used in
> organs (12 to 15 VDC) wouldn't always jump through any oil on the
> tracker bar ...

There is absolutely no reason for there to be any oil on the contact
roller as if there were is would be transferred to the roll paper.
Anybody who may have suggested this to you is obviously unfamiliar with
these machines.

The information I received on these matters came from two coinciding
sources.  First was from a Mr. Robert Weber who worked on the continuing
and ongoing design improvements of the Mills Violano Virtuoso machine,
and also the Professor Dr. Walter Reckless who was an employee that
performed a number of the parts of the rolls that were made during the
twenties.  He was a law student at the University of Chicago and worked
at Mills Novelty Co. as a musician among other things, in order to
finance his legal education.  He later became Law Professor at Ohio State
University in Columbus, Ohio.

I came into contact with him about twenty years ago through a personal
friend, Dr. Charles Mac Cluer, who is Mathematics Professor at Michigan
State University.  Chuck, who is also a fine professional blue grass
fiddler, used to spend hours listening to my Violanos and was kind enough
to keep me well supplied with slightly used fiddle string of the finest
quality, which no doubt helped the sound of them.

Musically yours

Hal Davis

 [ Thanks for your reply, Hal.  Before I comment further I'd sure like
 [ to hear from other folks who have worked with the Mills instruments
 [ and related electrical devices -- specific experience is usually
 [ more valuable than the generalities I wrote about. ;)   -- Robbie