[R-390] Meter Meister?

[Gene Beckwith]

Barry,

Excellent post...and a frustrating subject for the casual meter repairman...

Agree with ur assessment that sounds like pointer/vane is somehow out of
alignment...but the blowing technique is a good test...also have used a very
thin/narrow bit of paper to "Gently" touch, or prod the movement to check for
rubbing or scraping.  Btw...have found that on some "Hamfest" specials...that
the glass has worked loose and has pushed the pointer back against the
scale...sometimes, the glass doesn't look like it moved, but has been pushed in
enough to cramp the pointer...and stay jammed so the glass doesn't
"rattle...just another check Joe...but sure you thought of this one...it's easy
to fix...but again am sure u check this one because it's a classic...

Now...further questions...

Barry  . . . Do you have any pet suggestions regarding tools, and handling
techniques for these ultra delicate manipulations....I've used the "blowing"
technique to check for free movement,  bits of paper cut to small manipulators,
re-machined nut drivers to reduce over-all od...and re shaped screw drivers of
various breeds...and types...

In some cases I've had great success, but in others...seems the most common
meter repair problem has been an "apparently" open coil...yuk...not a good
situation...and have not had luck solving that one...even with resoldering micro
joints...so I assume in these cases, it must be open some place I can't isolate
other than the coil...

Just ramblings, but meter info always of interest...

73,

Gene

Barry Hauser wrote:

> Joe & List:
>
> If it isn't particles or a bad protective diode, it may be that the armature
> has come off one of its bearings or is loose.  Depends on the design, but
> many meters have needle bearings which are adjustable.  It's sometimes
> difficult to spot because just the very tip of the tiny shaft may become
> warn enough to slip out of center and jam.  Usually the needle won't move at
> all, but I've seen cases where they'll move partway in one direction.  If
> the meter has adjustable bearings, you can loosen a locknut and turn in the
> bearing slightly to tighten it up.  If that's the case, be careful not to
> overtighten and make sure the shaft lines up straight as you do so or you'll
> damage what's left of the pointy end of the shaft or bend it altogether.
> (Center the shaft somehow and just tighten a small amount, then blow on the
> needle to see if it swings freely.  If/when it does -- stop.  A bit too much
> and the needle won't move, then back off a smidgen.)  Often these adjusters
> are secured with a droplet of glyptol or cement. Usually a partial situation
> is obvious because when the shaft is crooked, the needle hits the scale, but
> sometimes it's the "tail" of the needle or some other part that binds
> because it rubs up against something, or even the spring itself gets out of
> sorts due to the misalignment. Those situations are not so obvious.
>
> Barry
>
> ----- Original Message -----
> From: "Joe Foley" <redmenaced@yahoo.com>
> To: <r-390@mailman.qth.net>
> Sent: Saturday, June 14, 2003 10:29 PM
> Subject: [R-390] Meter Meister?
>
> >
> > >
> > > I need someone to tell me what I just did to ruin
> > > this
> > > DC voltmeter.
> > >
> > > I was checking the voltage on a UPS when my Steel
> > > Six
> > > meter decided to crap out!  Not good, I liked that
> > > meter!
> > >
> > > 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.
> > >
> > > 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.
> > >
> > > Thanks,
> > >
> > > Joe
> >
> >
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