In article ,
jim rozen wrote:
In article , DoN. Nichols says...

Unfortunately, one of the nicest has an interesting plastic
gear inside to couple a switch to the knob on the front panel, and the
plastic has gotten brittle over time. I've seen two of those with the
plastic disintergating. I own one of them. I would love to see a
drawing of the gear's dimensions, with the hopes that I could make a
replacement. The plug-in is too nice to consign to the trash bin.

It is a barrel (perhaps 3/4" long), with a hex hole through it,
and a set of gear teeth only about 1/8" long in the middle of it.

Don, what is the model number of that particular plug-in?

O.K. Found it! I seem to have misremembered the dimensions of
the plastic gear. But it is in a 7A13 plug-in. The "Fine Comparison
Voltage" is two concentric knobs. The inner one turns a 10-turn pot,
and the three LSDs of a Veeder-Root style counter on the front panel.
(Lots of small plastic gears for that part.) The outer one turns the
MSD of the Veeder-Root counter, and it *should* also turn a 10-position
switch, but the gear collar is all gone (It took me a while to
remember/rediscover just what was missing and how it should work.) All
of the other gears are fine, but that one is long gone. The metal hub
(with setscrews) which it should be on has four ridges to give a bit
more grip to the gear so it can rotate the switch (which takes a
respectable amount of torque). The whole thing lives under a bent
aluminum shield in the upper-right hand corner of (just behind) the
front panel.

Wonderful construction -- but the materials were not up to the
stresses. All of the gears are a brown plastic -- a bit lighter than
Phenolic or Bakelite.. I'm wondering whether I can make some
replacements from Delrin, and how well they would hold up. (I first
have to figure the tooth pitch and the count.)

Thanks,
DoN.

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