Piano Electric Power Switch Shock Hazard
By Carl Zwanzig
[ Nigel Perry wrote in 1100704 MMDigest:
> Obviously a short. Removing the earth line to the motor casing
> solved that.
Hi Nigel, Unearthing the motor casing may have made the problem "go
away" but didn't fix a rather bad situation. That motor has a short
circuit, from the winding to the case, and needs a visit to the motor
Generally speaking, there should be at least 1 megohm resistance
from winding to case, and the case should be solidly earthed/grounded.
The fact that in most instruments the motor is mounted on wood
(non-conductive) and belted (also non-conductive) to the pumps doesn't
necessarily mean that it does not need to be earthed. The same goes
for any metal near a line/mains wire.
(Message sent Wed 6 Jul 2011, 19:27:10 GMT, from time zone GMT-0700.)