Hi folks,  All this talk of electrical safety in old instruments set me
off on a project I should have attended to many years ago.  After all, I
used to be responsible for the electrical safety of hospital equipment !

Although I no longer have access to a megger I do have a sort of
equivalent in an old Eico R-C comparator bridge, which itself is almost
antique.  It applies up to 500 vdc and gives usable indications for
leakages through resistances of hundreds of megohms.

 [ I remember that tester.  It has a type 6E5 "Green Eye" indicator,
 [ just like Grandma's old Zenith radio.    :-)    -- Robbie

So much for that.  The bottom line is that my 1922 Haines Ampico failed
the test.  Since I had replaced all but a 6-inch section of cord in the
rather over-designed plug-conduit arrangement between the line cord and
the motor & switch, I headed right for that.  Sure enough the leakage was
in that location.

The surprise was that it was not the wire.  It turned out to be the
pseudo-ceramic material that had been used to fill the holes behind the
contact mounting rivets in the ceramic socket connecting to the motor and
switch.  This material was in direct contact with the inside of the
(painted) conduit system.  The leakage was nowhere near a dangerous
level, but I thought that others might be interested as to where the
problem may lie if they apply a megger to similar materials.  In my case
the (non-)problem was solved by placing a piece of tag stock behind the
offending connector.

Jim Heyworth,
Sechelt, B.C., Canada
mailto:james_heyworth@sunshine.net