hosted on condor3913
 Mechanical Music Digest  Archives
You Are Not Logged In Login/Get New Account
Please Log In. Accounts are free!
Logged In users are granted additional features including a more current version of the Archives and a simplified process for submitting articles.
Home Archives Calendar Gallery Store Links Info

End-of-Summer Fundraising Drive In Progress. Please visit our home page to see this and other announcements:     Thank you. --Jody

MMD > Archives > June 1997 > 1997.06.25 > 07Prev  Next

Electrical Safety
By Robbie Rhodes

In normal use the motor circuit is controlled by the heavy switch in the
piano (in the drawer or spoolbox).  The switch itself dissipates the
energy stored in the motor winding as a big spark, but this surge doesn't
travel out the power cord.  However, if the piano switch is left 'on' and
the piano is controlled by an external switch or relay somewhere (as in a
pipe organ installation), then the big voltage surge leaves the piano via
the power cord.  Thus bad wiring between the power cord and the switch in
the piano could go undetected for years, only to wreck havoc after the
external relay is used a few times.

I suspect that the condition of the rubber insulation in the wiring is as
variable as in the rubber hoses elsewhere in the piano.  Once it hardens
from age and cracks, then dust and grime can seep through the cracks and
ultimately cause a flash-over when the piano is switched off.

A simple and cheap protection is the varistor surge protector, also
called voltage-dependent resistor (VDR).  This little disc-shaped device
is connected across the switch contacts and will absorb and dissipate the
energy which otherwise causes the big spark when the switch opens.

Robbie Rhodes

(Message sent Wed 25 Jun 1997, 12:20:30 GMT, from time zone GMT-0700.)

Key Words in Subject:  Electrical, Safety

Home    Archives    Calendar    Gallery    Store    Links    Info   

Enter text below to search the MMD Website with Google

CONTACT FORM: Click HERE to write to the editor, or to post a message about Mechanical Musical Instruments to the MMD

Unless otherwise noted, all opinions are those of the individual authors and may not represent those of the editors. Compilation copyright 1995-2022 by Jody Kravitz.

Please read our Republication Policy before copying information from or creating links to this web site.

Click HERE to contact the webmaster regarding problems with the website.

Please support publication of the MMD by donating online

Pay via PayPal

No PayPal account required

Translate This Page