Techniques for Repairing meters

[George Maier]

Mike:

Can't say why, but I've had a high success rate in fixing meters, and
I'm willing to share the few empirical tidbits I've gained along the
way.

First, get yourself a jewelers eye loop. You know, a monicle that
magnifies.

Once you have one, carefully examine the bearing of any meter that is
problematic. What I have usually found is dust, dirt, corrosion,
microfine hairs, etc, that are causing the pointer to bind, or limiting
its travel.  In a moving coil (D'Arsonval) movement, I've often found
metallic fragments inside the magnet.  In magnetic(vane) meters, usually
dirt, or microfine flakes from the inner case.  If you are very careful,
you can use a vacuum cleaner crevass tool to pull these fragments out.
It is imperative that you manually hold the pointer while you clean.

The key is a thorough visual inspection before setting your course of
action.  Recently I bought a Collins 302C-3 power meter only to find it
the pointer had become detatched from the moving coil.  A little super
glue did the trick, but it was a getting up close and personal that
revealed the problems.  Sometimes a tenth of a drop of super light oil
on the bearings helps (how you get to a tenth is a not easy [grin])

Not sure I've helped, but suffice it to say that meters require a
delicate touch, a lot of patiemce, and some up front study before making
a move.

Good luck..

George - K1GXT
Huttinger wrote:
>
> Hi all,
>     In the bad old days I had a Heathkit AT-1 whose meter died.  I tried in
> vain to fix it and over the years have tried to fix many other meters only
> rarely succeeding.  I just fixed one where the hairspring had caught under a
> crossarm and was giving non return to zero and return to various points on
> the dial besides zero due to the hairspring dragging across the crossarm.
> Are there any ideas for fixing meters that sometimes work?  Has anyone tried
> replacing the guts of a meter with a meter movement of the same full scale
> uA rating and used the dial face of the old one?
> Regards,
> Mike Huttinger
>
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