On Wed, 18 Mar 2020 07:31:34 -0400, "Jim Wilkins"
wrote:

"Richard Smith" wrote in message
...
writes:

On Sat, 14 Mar 2020 21:25:20 +0000 (UTC), Cydrome Leader
wrote:

Has anybody remagnetized a rotary on-off mag base before? I was
thinking
about a large capacitor and some turns of wire on EI transformer
core
with the Is removed and the indicator base across the center and
one side
leg.

How are these magnetized at the factory?
Probably your best bet is to replace the old alnico magnet with a
new
rare earth magnet. This is because if the alnico magnet is removed
from the magnetic circuit it loses a lot of its magnetism. The
alnico
magnets in old and/or inexpensive mag bases were/are magnetized
after
assembly. This takes a LOT of current. I have seen the setups for
doing this and they are not trivial.
Eric

I save the magnetising assembly at a magnet factory in Sheffield,
UK,
a long time ago.
Which leads me to voice agreement with Eric.
It fitted on top of a pallet, took some huge current, dust was
flying and their were major creaking sounds as enormous forces
resulted.
Rich S

I've built 1000A test stations for devices such as electric locomotive
controllers. The construction is considerably different from normal
electronics, requiring copper buss bars, crimpers for 4/0 welding
cable lugs, mechanically strong and heat resistant insulators etc. All
conductors must be well supported to resist the magnetic attraction
between them and to the steel chassis. Common test equipment won't
measure the high currents or microOhm resistances involved.

My personal test gear collection includes second-hand lab grade and
new import hobby grade shunts like this
https://www.amazon.com/AMMETER-SHUNT.../dp/B005BHPG6K
to measure AC and DC current and a 1000V hipot tester to find
accidental shorts or leakage, mainly keep shocks or exploding wires
fom putting me in the hospital.


Reminds me of the old mag cells. A building was a row of pots up one
side and down the other electrically in series, running at about
30,000 amps. The workers commonly stored their tools by just slapping
them on a buss bar above a cell. There was a massive tool drop every
time they took a cell building down.