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    Potentiometers tone controls Pas2-3, for Option X?.

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    Pillo69

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    Potentiometers tone controls Pas2-3, for Option X?.

    Post by Pillo69 on Sat Feb 18, 2017 2:17 pm

    I have removed a control potentiometer from a PAS2.
    The rear body has a grimace to stop the course.
    Tested in the center (between 0 and 750k) without the stop, it gives continuity between the three terminals. It also has a few small ohms between them.
    This position can be similar in operation to model "X"?















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    Pillo69

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    Join date : 2012-04-11
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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by Pillo69 on Sun Feb 19, 2017 11:59 am

    No one knows about the performance ?.
    I'm going to ask in other audio forums.
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    PeterCapo

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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by PeterCapo on Sun Feb 19, 2017 12:13 pm

    Not exactly sure what you are asking.  But, the tone control pots were different in the PAS depending on whether or not the X-mod is present.  Have a look here: http://www.audioregenesis.com/documents/Dynaco%20PAS%203%20or%203X.pdf
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    audioregenesis

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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by audioregenesis on Sun Feb 19, 2017 1:31 pm

    If you are asking if this particular 750K (bass) potentiometer, set to this precise position, will perform the bass bypass function, essentially, yes it will. However, from the practical standpoint there are numerous issues:

    - The wiper connection bridging the pot. endpoints is nebulous at best, and would need to be very precisely set. It may not even be attainable for all other pots of the same type.

    - This exact position would only be possible if the stop were eliminated, either by removing the cover, or modifying it to delete the stop. This would mean the pot. has 360 degree rotation. Attaining the reference center position, as described in the assembly manual (P-13) would present a problem.

    - Relative to the bypassed position, even a slight deviation would result in immediate full bass boost or full cut, depending upon the direction the pot. was rotated, not a gradual boost or cut, as exhibited by the 3X pot.

    The actual 3X bass potentiometer is of completely different construction, designed specifically for its purpose.
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    Pillo69

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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by Pillo69 on Sun Feb 19, 2017 2:18 pm

    By removing the top of the body, when the potentiometer travels to that position it descends, so its position is noted.
    The treble potentiometer works the same.
    I do not know if that function of the treble potentiometer should be this way. I'll look at it.
    The modification is simple, remove the stop.
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    audioregenesis

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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by audioregenesis on Sun Feb 19, 2017 3:13 pm

    It's true that the wiper will descend as it passes into that position. However, the wiper is curved, and and thus makes contact with with only a very small portion of the conductive material presented at the very edges of the wafer. To get the best "connection" it must be well placed. I actually just took apart a PAS 2 bass potentiometer and did some experimenting.

    I found that just going by the "feel" of the small indent exhibited at that position, sometimes the resistance between the pot end points was less than 100 ohms, sometimes it was several K ohms, or even 10's of K ohms. So, on this particular, pot, I had to look at the ohm meter to find the lowest resistance point. This is what I meant by the connection being nebulous, and the need to be positioned very precisely. I would expect some variation from sample to sample. The conductive coating at at end points of the pot is also very thin. It was never meant to have the wiper passing over it as a matter of normal operation, so it's also possible that it may not hold up over many operations in and out of that position.

    While it's interesting that the wiper actually does (barely) manage to connect the end points of the pot, when set to this position, in the practical sense I would not count on it to provide a proper and complete bypass each and every time.

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    Pillo69

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    Re: Potentiometers tone controls Pas2-3, for Option X?.

    Post by Pillo69 on Sun Feb 19, 2017 3:33 pm

    Perhaps a cut with a dremel to the sides of coal of the potentiometer?
    I will try, it will not hurt because with the top it will not get there.

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