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

Sorry for the OT. I made a mistake, and posted the mesage on the wrong
newsgroup.

Tony I0JX

On Fri, 8 Dec 2006 21:11:44 +0100, "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.

Hi Tony,

Consult paragraph 5-5:
http://www.rigpix.com/hallicrafter/sx117_manual.pdf

73's
Richard Clark, KB7QHC

Consult paragraph 5-5:
http://www.rigpix.com/hallicrafter/sx117_manual.pdf

73's
Richard Clark, KB7QHC

Dick,

you read my question too quckly. I was not referring to the electrical
adjustment (there is a potentiometer just for that) but to the mechanical
adjustment.

In a properly maintained radio, the meter should stay at zero even when the
radio is off. That is the reason for the mechanical adustment.

73

Tony I0JX

On Fri, 8 Dec 2006 22:19:15 +0100, "Antonio Vernucci"
wrote:

you read my question too quckly. I was not referring to the electrical
adjustment (there is a potentiometer just for that) but to the mechanical
adjustment.

Hi Tony,

From paragraph 5-5 "The Meter Zero control may be found directly under
the rear of the meter housing."

73's
Richard Clark, KB7QHC

Hi Tony,

From paragraph 5-5 "The Meter Zero control may be found directly under
the rear of the meter housing."

73's
Richard Clark, KB7QHC

Again Dick, I have adjusted that control many times and any SX-117 owner knows
that that contriol exists.

I am instead trying to adjust the mechanical zero which has nothing to do with
the control under the rear of the meter housing. Do you appreciate the
difference?

Tony I0JX

On Sat, 9 Dec 2006 10:49:08 +0100, "Antonio Vernucci"
wrote:

Do you appreciate the difference?

Hi Tony,

Nope.

The meter is always in a condition where current is flowing given that
it shares the cathode load. Paragraph 5-5 says quite clearly how to
set zero for a zero signal condition. Basically, the design reveals
an admission that there is no "zero" in the first place (merely a
minimum).

Aside from that, there is no need to be concerned about a meter
reading for a receiver that is turned off. In short, any attempt to
force a mechanical zero would be negated by the "electrical zero" set
and S-9 calibration.

73's
Richard Clark, KB7QHC