Mark Kinsler wrote in 200403 MMDigest [about the MIlls Violano]:

> I would have thought that the manufacturers would have bridged the
> contacts with capacitors, which was formerly the preferred means of
> contact arc suppression.

There is no need to.  The end of the note hole in the paper roll on
the Violano separates the contacts and acts as a capacitor.  It is
different if you try to separate two contacts which simply have air
between them when separating.  The air ionises and the arc continues
for a while.  If separated by a dielectric other than air, the arc
is immediately quenched.

On the Violano the sensing contacts are thin pieces of copper wire
above the paper roll which contact a metal roller below it when a hole
in the paper arrives.  If a sensor were to touch the roller without any
 paper in place the wire would vaporise when trying to separate, but
the presence of the paper prevents this.

If one switches the machine to play without a roll in place then of
course all the contacts would touch the metal roller at the same time,
but in that eventuality the power supply would be hugely overloaded,
the voltage would drop down to almost nothing, and the main fuse would
blow.

The problem of wire melting would generally only occur if someone
attempted to test each note by touching each sensor note with a probe
to see if the note played.  It's fine when you touch it, but when you
remove the probe vaporisation occurs!  That is why a test roll is about
the only way to check each note.

Bear in mind that inductors (coils etc) draw virtually no current at
the instant when a voltage is first applied but attempt to keep the
current flowing when the voltage is removed.  Capacitors act exactly
the opposite, so putting capacitors across the contacts would most
probably increase the contact sparking.

Many of these machines have been operating for 50 or more years without
appreciable wear to the contact wires, so if it ain't bust, there is no
need to fix it!

Regards,

David Evans - Nickelodeon Museum
Cowichan Bay, British Columbia, Canada