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Re: [TenTec] CorsairII notch potentiometer

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] CorsairII notch potentiometer
From: "Charles P. Steinmetz" <charles_steinmetz@lavabit.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 10 Feb 2011 03:46:04 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Steve wrote:

>The pot mounts directly to the PCB, so swapping the ends means cutting
>tracks

I thought I gathered from your description that you actually ended up 
using wires to extend the pot leads.  Or maybe I misread?

>The front panel is marked with an "Out" position with the knob fully
>CW; in that position the AF frequency of the notch is above the filter
>passband. Reversing the "sense" would mean that in the "Out" position
>the notch is still within the passband, albeit at the LF end and maybe
>not too noticeable.

Couldn't you just remember that the "out" position was at the CCW 
end, same as you'd remember that the frequencies were reversed from 
their normal relations?  If the now-extraneous panel marking bugs 
you, you could cover it with tape -- or if the panel is metal with 
silkscreened graphics, some methylene chloride and a Q-Tip will take 
it right off (if the front panel has a plastic overlay, don't try this).

>All of this makes me wonder why TT went to the trouble of using a
>reverse log pot.

Because (i) they wanted geometric tracking [thus, log] and (ii) most 
people think it's natural to get higher frequencies by turning a knob 
CW, just like it's natural for a PBS control to shift towards the USB 
in the CW direction and the LSB in the CCW direction [thus, reverse].

I came late to this discussion -- did you try to get an exact 
replacement from TT, and they don't supply them any more?

Best regards,

Charles




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