Phil Nelson wrote:
Is this something a fumble-fingers like me could attempt? What's involved in
making a movement right resting? I have little to lose at this point . . . .
Assuming you're not serious about "fumble-fingers" - it is likely
"doable" - though it takes a LOT of patience and you will sacrifice some
accuracy (though IIRC the S-meter system in those radios were "relative"
anyway).
First you want to determine what type of meter movement it is -
hair-spring (likely), taut-band, or other (not likely). If it's a hair
spring (spring that spirals in - in a flat plain) and has both a front
and rear adjustment- then it's likely you can successfully "re-zero" it.
The front spring mount usually has a large loop adjuster that is often
engaged by an eccentric pin from the face that allows external zero
adjustments- the rear usually also has an adjustable spring mount - but
far more "dainty" as it's not intended for frequent adjustment - in fact
most are never touched after first calibration when made. It's this back
adjustment that you want to CAREFULLY turn until you zero the meter at
the right. Be very careful to not kink the spring, etc. - most meters
will have enough play to run them fully across using only the back
adjustment - though with some - you may have to use some of the front
adjustment as well. Since the meter will now be "unwinding" the springs
rather than winding it - the meter's linearity will be less than it
should be - but in this application - I doubt anyone would notice. Just
be sure and check for clearance around both springs as they flex as the
needle swings -- as again - the springs will be "un-winding" now rather
than "winding".
Once reversed - you'll have to experiment some to see how it reacts -
whether it appears that the indicated reading is what you would expect -
or if you need to "adjust" the circuitry a bit to better "calibrate" the
system.
HTHs -
--
randy guttery
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