[Test-Equipment] An interesting meter repair

[k0xp@dandy.net]

>With the pointer locked, a careful inspection under a 
>strong light of the internal aspect of the left magnet 
>pole ajacent to the armature bobbin showed what appeared 
>to be a bright orange irregular patch corresponding to 
>the position of the interference.
...
>It took about 1/2 hout to completely free up the stuck 
>movement, with a little extra sanding and polishing for 
>good measure. The result is a perfectly working meter, 
>earlier deemed unsalvageable!

First, congrats on your perseverance and success, Art!

Second... very frequently, meters stick because of a very tiny sliver of metal 
or wire stuck somewhere on the magnet which catches the coil bobbin. As the 
coil moves back and forth, it catches and moves the sliver which sometimes 
causes the pointer to stick in other locations. A jeweler's loupe works wonders 
when trying to see these foreign particles. In mine younger days, I got pretty 
good at seeing and removing these; today, I can still just barely see them but 
the time is coming when mine eyes just won't be able to hold a focus long 
enough. Now I know what my Elmer was complaining about as he got into his 
"golden years" and I had to take over more and more of the construction around 
his station  ;o((((

>I would like to hear if anyone else has encountered this 
>kind of a problem, and what the cause might be. There was 
>no evidence of moisture anywhere, and I am at a loss to 
>explain the rust/corrosion/fungus that I observed.

Really cannot explain it other than to suggest that if a meter is not 
hermetically sealed and evacuated, and is transferred from a cold to a hot 
environment with no opportunity to slowly warm up, I'm certain that moisture 
will condense inside the case, just as on your eyeglasses. Moral: use or leave 
your equipment in one or the other environment, or transfer them from one to 
the other while letting them warm up slowly, not suddenly. The use of dessicant 
sacs inside some equipment helps, too, if you have a way to dry them out every 
so often.

73, Steve
K�XP