There was a recent posting about a catalog from HB Electronics via
snail mail. Here's a note on their variable capacitors.
Some time back I got e-mail from them with a special deal on some
Cambion panel-mount air variable caps for a buck each (which are
still in their catalog). Although I have "tons" of caps already, he hit
me at a weak moment so I ordered a dozen of various values, sight
unseen. He did give the Cambion part number (type 563-7637- ##),
but I was too lazy to look them up somewhere. The e-mail said that
they were screwdriver adjustable but could be converted to knob use
with a Dremel and a cutoff wheel. You can also do it with a hack saw,
though. (Their catalog now contains what appears to be the same type
of capacitor but with a 1/4" shaft, for $4 each, in addition to the
screwdriver adjustable type at one buck. I have no idea whether these
are made differently or if he just chops down the bushing himself, but
either way it's a big difference in price and well worth a bit of
hacking!)
These caps are single bearing, the type with a slab of ceramic material
as the body (a little over 1 X 1.4", and 0.16" thick), with stator bolted
to it. As they come out of the bag, the mounting bushing is about
0.58" long and the shaft (with screwdriver slot in the end) is about
0.65", leaving about 1/16" for your knob. (The bushing is tapered and
slotted at the end, for use with a shaft locking nut which is provided.)
Due to the construction, you can shorten the bushing and get some
space for a knob or coupler. You can get up to about 0.55" of shaft,
although that leaves no thread for mounting to a panel by way of the
bushing and a nut--you'd have to use screws and nuts thru the holes in
the ceramic.
There's nothing welded or soldered--the caps are assembled only with
nuts and threaded studs, and you can take them apart completely with
a screwdriver and a pair of pliers. Disassemble completely, taking
care to lay the parts out in the proper sequence so you don't spend 10
extra minutes figuring how to reassemble it. I found it necessary to
remove the stator as well, to provide clearance when removing the
bushing from the ceramic.
Take out the bushing, put one or more nuts on it, down all the way,
then cut off as much as you want with a hacksaw. If you forget to put
on a nut or two first, you'll have a much harder time during
reassembly, trying to get the nuts back onto a hacked-up thread.
Another important consideration: remember that when the bushing is
put back in place, it must have enough thread left to accommodate
the thickness of the ceramic body, the nut to hold it to the body, panel
thickness and a final nut to hold it all to the panel (and maybe a
washer as well). Don't cut off too much like I did on the first one!
If you prefer to leave the stator in place and save some work, just
remove all of the rotor parts and shaft, leave the bushing attached to
the ceramic plate and cut it off that way. (But be careful how you hold
it, so you don't crack the ceramic--secure the slotted end of the bushing
in a vise, don't clamp on the ceramic.) Again, be sure to put a nut on
it before cutting to clean out the threads, and leave enough length to
accommodate all nuts and panel thickness.
If all of this is too much work, you can fall back on a variation of the
Dremel method, which is to use a hacksaw, cut into the bushing until
you just hit the shaft, rotate the whole thing slightly and repeat until
you've gone all the way around. It won't be as pretty, but should
work.
Their addresses--hb.electronics@businesson.com for e-mail and
www.businesson.com/hamparts for you webbers.
Usual disclaimers; he's not a friend or a broher-in-law, I don't have my
401K money invested in him, etc; I have no connection with HB except as a
customer.
73 and Queue Our Pea DE WA8MCQ wa8mcq@abs.net
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