Paul S. wrote
"The pots on the digital counter and its actually quite small. The 3
leads all fit into an area about the size of a pencil eraser."
Yeah, I know what you mean. I had assumed the pot in question was one of
the more modern, fairly compact ten-turn helipots, that are about an
inch diameter and length (body size), as opposed to the really big
old-school ones (about 2" D and L). There is at least one style even
smaller, about 1/2" D x 1" L. These are true helipots, built with a
helical mandrel carrying many turns of fine resistance wire. Below this
size range, I don't know if a helical pot structure can be built
practically, so it's possible that these small clock face style ones may
be more similar to the small multi-turn trimmer pots, with a short,
straight mandrel, and the wiper driven linearly by a worm-screw
mechanism. The difference in construction has a huge effect on available
resolution. A helipot will have one loop of mandrel for each shaft turn,
so its effective length is quite large, compared to a short, straight
element, with gear reduction to provide multiple turns.
Regarding the 5065A, I suppose the clock style pot was for saving space,
with the pot actually inside the knob and counting assembly, and hardly
anything behind the panel - pretty slick. I think I still have somewhere
the actual pot from the 5065A carcass I got many years ago (used to
build Z3801A into), and I just found a few of probably the same kind,
that I had collected over the years. The whole front is a knob about
3/4" D x 1" L, with a clock face (except 10 vs 12 points) readout in the
tip. The back looks like a standard 3/8" D mounting shank, with only the
pot terminals sticking out.
So, it's possible that they managed to squeeze a helical pot mechanism
and readout in there, but it could be something else. I've never had any
of these apart (which probably requires destruction), so don't know
what's in there. One way I could picture it working, is that the knob
itself is the wiper carrier, shaped internally with the right screw
pitch. The mandrel could then be wrapped around an inner structure, and
the readout mechanism in the center and tip. Another option is that it
could be helical, but not necessarily ten full turns-worth - maybe five
turns, and 2:1 mechanical reduction, and so on.
I think these kinds likely are still made, so data sheets may describe
or show what's inside.
Ed
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
