[Premium-Rx] WANTED: 20 turns precision potentiometers

[Ahmet Gundes]

Andree,

You might want to consider using 2  10 turn pots and add a switch to switch the
second one in when the first one runs out of turns. 20 turn pots are quite
expensive. not easy to find. some of the old Tektronix test equipment (scopes
especially) had some 10 turns but never seen 20s. if you use two 10 turns you can
save money and get the same job done basically.

I don't know your circuit but maybe a stepper motor controller as precise as
0.5 Degrees will do the job. have you considered those.  you can get a stepper 
motor with a 1 degree control accuracy and a controller for about $ 40 range.
But of course it all depends on what kind of circuit you have.

How did they control the servos ? they use the voltage from the pots to determine
the position ? best way to get accurate results is to use microcontrollers these
days. but in the old times they did not have such precision i think.

it is a pain in the neck to fix, allign and design with gears. requires too
much precision. 

regards, ahmet


> 
> Dear Greg,
> 
> please place this at Premium-RX,
> 
> thanks, Andreé DD3LY
> 
> 
> 
> Dear List members,
> 
> I am looking for 20 turn precision potentiometers. Surely you all 
> know those 10 turn potentiometers which are normally used in test 
> equipment. These 10 turn potentiometers are about 1 inch in 
> diameter and 1.5 inches long.
> 
> But what I am looking for, are precision potentiometers with 20 
> full turns, each turn with 360 degrees. Such 20 turn potentiometers 
> have about twice the length of a standard 10 turn potentiometer. I 
> own one 20 turn potentiometer wich I took from a Varian SHF 
> downconverter. So these potentiometers really exist! But even the 
> one I own is defective :-(
> 
> I would like to find three or four 20 turn potentiometers, which 
> may be used but should be in good working order. The value of the 
> maximum resistance is not really important, something between 1k 
> and 100k will be OK.
> 
> The reason why I look for these is that I want to use them as a 
> servo position indicating potentiometer in a modified professional 
> preselector where two variable elements are motor driven. There 
> were plastic gears between the main axis and the position 
> potentiometer. Both gears are defective now and cause faulty 
> position indication. If I place a multiturn potentiometer with 20 
> full turns on the main axis, all tolerances will be reduced to 
> ZERO. This would be fine.
> 
> Thank you for digging through your "junk boxes".
> 
> With Greetings from North Germany
> 
> Andreé DD3LY
> 
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