[ 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
repair shop.

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.

z!
Carl Zwanzig