According to jim rozen :
In article , DoN. Nichols says...

2) To keep metal filings from the workbench from jumping up to the
magnet (which can jam the meter movement -- I've seen it
before).

Common indeed. The key to repairing a moving coil meter like that
that's jammed from magnetic swarf in between the pole pieces, is to
simply unbolt the magnet from the movement.

[ ... ]

Once it's off the movement, blow or brush the debris out of the
way.

Indeed so.

I've unstuck a bunch of simpson meters with hang-y meters this way.

The diodes BTW are protection diodes. They prevent the coil from
blowing out by shunting any voltage more than 0.7 volts around
the meter.

Well ... in this case, 2.1 volts, as there are three silicon
diodes in series. (Even without looking them up, I know that they are
not germanium diodes, because only the silicon ones have their glass
cases painted black -- presumably to eliminate photoelectron
generation.

Enjoy,
DoN.

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