Use a "rack & pinion" type of set up with the
shaft, and a right angle drive out the front panel.
The "rack" would be the sliding shaft, the pinion
would be the shaft going to the bandswitch knob.
The "rack" could also be made of something "non"
metal and maybe put right through the center of the
inductor.
Mark WB8JKR
On Thu, 12 Oct 2000 13:38:55 -0700 "Colin Lamb" <k7fm@teleport.com>
writes:
> Here is a proposal for an alternate bandswitch design - to eliminate
> the arcing problem between the contact and rotor.
>
> In the simplest form, imagine a 1/4 inch metal shaft coming out of
> the front panel of your amp. It would go through a bearing which is
> grounded. As you pushed it back, it would contact more and more
> contacts and ground those points. Spacing could be very high.
>
> The problem with this design would be that: (1) you normally do not
> ground the switch points and (2) a lever sticking out of the panel
> is an invitation for disaster. But, once the concept is understood,
> those problems can be solved.
>
> Let us then rotate the shaft vertically and instead of a push - pull
> shaft out of the front panel, a knob would be placed on the front
> panel and parallel to the shaft, which would actuate like a sliding
> volume control. As the knob went up and down, it would move a shaft
> that would "short" out additional contacts. Detents would be in
> place to assure positive stops. Now, because the shaft is not
> exposed, we need not have it grounded. Instead, it could be
> insulated from ground with the coil right behind it to short out
> progressive taps.
>
> One negative is that it would not easily allow engagement of a
> conventional switch for the cathode input circuit. It would work
> well with untuned input or a similar arrangement could be ganged for
> the tuned input circuit. Or, a parallel shaft could operate remote
> relays for the input circuit.
>
> 73, Colin K7FM
>
>
>
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