[R-390] Meter Meister?

[Bill Smith]

Sounds to me like something is open.  Set an ohmmeter on a high scale, then
measure from outside terminal to resistor, through resistor, to meter, then
to the small terminal that holds the spring, then to the other side of the
meter (watch meter movement here), etc.  Test from both meter terminals.
The meter current passes through the springs to the wiring in the armature.

Have found metal-to-metal contact can still be an open electrical path,
particularly the hardware between the meter bridge and the spring.
Sometimes just moving things around will break down oxidation.  Don't think
that is the case with yours, though.   You might look for a broken or
disconnected spring (though that would affect meter zero), or open armature.
If you see a lot of life in the meter movement (let's all hope) then one of
the series resistors has opened.

If the armature is open, you might try looking under a very strong
magnifying glass (as in a lab microscope) to insure the wire contact between
the armature and spring terminal is still intact.  Have fixed a meter or two
by reattaching a loose or broken wire end.  The wire size is extremely
small.  Of course that is a very delicate operation.

If the armature winding is broken somewhere inside the winding, that may be
fini, would be for me.

73 de Bill, AB6MT
billsmith@ispwest.com




----- Original Message -----
From: Joe Foley

Nope, no ranges, no resistors except the two coils on
the back panel.

One wire goes directly from the terminal on the side
of the box to one end of the coil, the other wire goes
from the other terminal to the two resistor/coils in
series, then to the other end of the coil.  Simple,
very simple,....... just doesn't work much.

Reverse needle movement doesn't peg, only about the
same as forward movement.


--- Barry Hauser <barry@hausernet.com> wrote:
>
> Joe wrote:
> > BTW, there are three tiny balancing nuts
> > on the needle placed at 90 degrees apart from the
> > needle itself.
>
> Sounds more complicated than usual.
>
>   Mostly it's a bare meter movement.  I
> > have a similar DC current meter to pair with it if
> I
> > can keep it working.  The needle is free, responds
> to
> > full scale with the puff test, smoothly, too.
>
> Probably not particles or misalignment of the
> armature then.  Sometimes I've
> come across such severe static that a meter won't
> zero -- just hangs
> wherever you point to on the "glass".  (Mostly
> happens with plastic lenses.)
> I doubt if that's it given the vintage and so on and
> that usually clears up
> sitting around or when subject to some current.
>
> Have you tried running the meter out of it's case?
> Does it have a range
> switch with precision resistors. Maybe one is bad.
> You said it won't go
> above 2 volts, but will peg with reversed polarity
> -- how much swing between
> zero and "peg left"?  Might be 2 volts or less.
> Does it have other ranges?
>
> Barry
>
>
>
>
>
>


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