[time-nuts] TAPR "PulsePuppy" Pot Selection

Angus not.again at btinternet.com
Sun Dec 24 19:39:21 EST 2017


Hi,

Normally it's best to adjust a multi-turn trimmer in just one
direction, so if you do overshoot, go back 2 or 3 turns and then on
again to the place you want to be. The imperfections in the mechanism
will drive you nuts (in a bad way) if you try to do fine adjustments
back and forth.

It's even better if you can monitor the wiper voltage when adjusting
it.

Angus.

On Sun, 24 Dec 2017 16:26:43 -0600, you wrote:

>I think I need to clarify what I mean by "backlash".  It is not simple free play in
>the adjustment mechanism- it is something much more irritating, as follows:
>
>I sneak up on the desired result, but manage to overshoot slightly.  So I back
>off on the screw, and find that at first the result continues to change in the
>*original* direction (making the overshoot even worse) for a bit before finally
>reversing as I wanted it to.  This behavior is not conducive to having a good
>time making critical adjustments, nor does it lend any confidence in the stability
>of the adjustment in the face of handling.
>
>Dana
>
>
>On Sun, Dec 24, 2017 at 4:06 PM, Charles Steinmetz <csteinmetz at yandex.com>
>wrote:
>
>> John wrote:
>>
>> I didn't really notice much backlash, though when setting oscillators I
>>> try to approach (slowly) from one direction until it's "good enough" and
>>> then stop, to avoid that problem.
>>>
>>
>> The hot tip is not to just "sneak[] up on the sweet spot and then walk[]
>> away," as Dana put it.
>>
>> Anytime you have an adjustment with some hysteresis (classic example is
>> setting a d'Arsonville movement to zero), you want to sneak up to the
>> perfect setting and then run the adjuster *back* the way you came just a
>> touch, to leave the adjusted part on its own without any mechanical
>> connection to the adjustor mechanism.  Such contact is almost always the
>> culprit if the adjustment drifts after you set it.
>>
>> This takes some "feel" for the motion of the adjuster mechanism, but it is
>> well worth investing the time to learn it by repeated trials of the
>> adjuster before you leave it alone.
>>
>> Dana is spot on with his advice to tap the board (or whatever mechanically
>> supports the adjusted part) to make sure it doesn't drift.  If it does, you
>> either failed to pull the adjuster out of contact with the moving adjusting
>> part, or the adjusted part just can't hold its setting.  In either case,
>> better to know that now than after you button the instrument back up.
>>
>> Best regards,
>>
>> Charles
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/m
>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>_______________________________________________
>time-nuts mailing list -- time-nuts at febo.com
>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.


More information about the time-nuts mailing list