[R-390] Meter Meister?

Sun, 15 Jun 2003 20:36:26 -0400

Bill,

Another great post...re the sticky tape...I tried the sticky portion of a post
it...with some scucess...but like ur tape suggestion too...

What kind of "probe" do u use to manipulate the spring...?

Thanks for any info...

Gene

W8KXR

Bill Smith wrote:

> ----- Original Message -----
> From: Joe Foley
> To: [email protected]
> Sent: Saturday, June 14, 2003 7:29 PM
> Subject: [R-390] Meter Meister?
>
> >
> > I need someone to tell me what I just did to ruin
> > this
> > DC voltmeter.
>
> You probably didn't do anything, but you can fix it.
>
> >
> > I was checking the voltage on a UPS when my Steel
> > Six
> > meter decided to crap out!  Not good, I liked that
> > meter!
> >
>
> Many meters have this problem.
>
> > It seems to have either demagnetized the magnet or
> > magnetized the vane, not sure  which.  The coils are
> > Ok because when I reverse the probes the needle is
> > drawn below zero, it just won't go above about 2
> > volts
> > on a 50 volt scale.
>
> Nope, the problem is likely a very small iron fragment that is jamming the
> mechanism.
>
> >
> > If there was an AC component on the DC I was
> > measuring
> > would it have done this?  The charger was on, I was
> > trying to determine if the batteries were charging.
> >
>
> Nope.  Here is how you return the meter to service:
>
> (1) take the meter apart, exposing the mechanism.
>
> (2) prepare very thin strips (1/16") of regular Celophane tape.
>
> (3) With (stainless steel) tweasers or some other tool, run the thin strips
> along the armature, and between the magnet and the meter windings.  Metal
> particles will stick to the adhesive on the tape.   Examine the strips.  If
> there is the slightest fragment on the strip, replace it with a new strip,
> and continue until the strips come out clean.
>
> Change strips often, for particles can be rubbed off the strips can
> re-contaminate the meter movement.  This operation is best done under a
> magnifing glass.   Be careful not to damage the spring or you may really
> loose the meter.
>
> (4) Gently blow across the meter scale, moving the pointer.  You should be
> able to very gently position the meter pointer at any point on the scale
> without touching it.  If it sticks at any point, there are still magnetic
> particles jamming the mechanism.  Continue cleaning with additional tape str
> ips.
>
> (5) When the movement is free, clean the inside of the glass and reassemble
> the meter.  It will work as new.
>
> (6) If you did crunch a spring (there are two, one on the top and another on
> the bottom of the movement), use a small pointer to very gently bend the
> anchor points so that the spring doesn't rub against itself at any point.
> It should form a level, symmetrical spiral about the pivot.
>
> Resetting the spring is a very delicate operation that takes some
> experience.  If you are working with a valuable meter, you might practice on
> another meter first.
>
> 73 de Bill, AB6MT
> [email protected]
>
> > Thanks,
> >
> > Joe
>
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