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Old February 10th 05, 07:32 PM
Antonio Vernucci
 
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I found the table. The original potentiometer behaves as follows:

Reading on scale Ohm
10 55
20 175
30 360
40 825
50 1200
60 1700
70 2190
80 2900

The scale on the panel is LINEAR. Of course I could paste a non-linear =
paper scale on the panel, thus emulating the non-linear potentiometer. =
But if one tries to do so, he will immediately realize that an important =
part of the scale gets highly compressed, with difficulties in =
accurately setting the knob to where indicated by the book.

Thanks for the suggestion to use a standard potentiometer that =
approximately has the same behaviour and to paste a paper scale to =
compensate for the difference. However, I will have to verify two =
things:

- whether potentiometers having a similar behaviour can really be easily =
found
- how much power the original potentiometer was supposed to dissipate. =
It may not be easier at all to find high-power carbon potentiometers=20

73

Tony, I0JX

"Scott Dorsey" ha scritto nel messaggio =
...
Alan Douglas adouglasatgis.net wrote:
The pot is nonlinear and the dial scale is also, so the resulting
curve defies logic. But all Hickok bias pots have been the same,
pretty much, since the 1930s. There is -40V across the whole pot, =

and
-3V at a dial setting of 20 (22 for the military TV-7).

=20
I am thinking that if you could use a standard antilog or log pot
(would a 5K audio taper be close enough?) you could then change the =

dial
scale accordingly. If you are willing to change the dial, you only =

have
to get reasonably close to the original taper.
--scott
--=20
"C'est un Nagra. C'est suisse, et tres, tres precis."