Hi, Tony

I have a "Shurite" brand iron vane panel meter, similar to what you
describe. The meter's zero adjust screw is connected to a semicircular
metal disk mounted at a right angle to the axis of the pointer shaft.
There is no contact between the semicircular disk and the pointer
assembly. I suppose zeroing is based on adding or counteracting
residual magnetism in the fixed iron vane. I don't see any torsion
springs in the Shurite meter.

An iron vane meter was used in the Heath DX-35, and I remember the
underdamped response. You could practically monitor your sending by the
sound of the meter pin hitting the end stops.

73,
Ed Knobloch

Antonio Vernucci wrote:
I opened the meter of an Hallicrafters SX-117 to mechanically adjust the
zero.
Once open, the meter appeared to be of the moving iron type, that is
with no
moving coil. But I was surprised to see that that meter has no spiral
torsion
springs either; I can only see a metal (?) dish mounted on the axis,
part of
which lies inside a rather flat coil.

With no spring, I cannot understand what forces the needle to stay at
zero scale
in absence of current. Therefore I cannot figure out what I should do to
adjust
the zero.

The HT-44 as well as the EICO 723 use the same type of meter. Dumping is
poor,
and the needle keeps banging for a while when you apply a DC current.

73

Tony I0JX