[R-390] Meter Meister?

Sun, 15 Jun 2003 00:29:27 -0700

----- 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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