B1M potentiometer

Discussion in 'General Electronics Chat' started by atlantis43, May 7, 2014.

  1. atlantis43

    Thread Starter New Member

    Apr 30, 2014
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    wondering if anyone can tell me if the leads on all B1M pots should correspond to one another, no matter the manufacturer?
     
  2. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    As far as I know the middle one, in common pots is always the slider.

    Show a picture of the one you are thinking of.

    Still struggling with that pot?
     
  3. atlantis43

    Thread Starter New Member

    Apr 30, 2014
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    Yes: finally found the markings on the pot switch! There was a microscopic B1M on it, for which I needed a jewelers loop.
    Can't send a pic, as I dismantled the original, but wires were connected to lugs 2 & 3.
    I got a new B1M pot-switch, and on the original the wires were connected across lugs 2 & 3.
    My question regards whether my new unit will perform like the old one if I make the same connections------or do any pots function in reverse?
    Hope that my question is understandable.
     
  4. #12

    Expert

    Nov 30, 2010
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    Some pots work, "backwards" but a linear, 1 meg pot is just so simple that i think I must have missed some other thread to understand why you have doubts.
     
  5. atlantis43

    Thread Starter New Member

    Apr 30, 2014
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    Glad to know that. I just wasn't sure if any were constructed in reverse.
    Thanks
     
  6. #12

    Expert

    Nov 30, 2010
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    The key word here is, "linear". The resistance changes in an even rate from one end to the other. In other words, a linear pot can't be backwards, only pots with a different rate of change can be backwards.

    There is a particularly famous, backwards, 3 meg pot used in Fender guitar amplifiers but you must be able by now to recognize that it must be an audio taper or it couldn't accomplish working backwards.
     
  7. atlantis43

    Thread Starter New Member

    Apr 30, 2014
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    having replaced the B1M pot switch, I find that the dimmer switch now works, but it appears that the bulb never seems to dim to as low a level as previously (with the original switch).
    I assume that the maximum resistance of both pots is 1MΩ, is it possible that the minimum Ω of this new pot switch is different than the original?
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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    Maximum resistance = lowest light level.

    Compare maximum resistance.

    All pots I've seen go to 0 ohms.
     
  9. atlantis43

    Thread Starter New Member

    Apr 30, 2014
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    Shouldn't all B1M pots have same maximum resistance = 1M, or is there something I don't understand about the designation B1M ?
     
  10. #12

    Expert

    Nov 30, 2010
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    There is tolerance error. Most pots are guaranteed to +/- 10% of the rated value, and, unlike inwo, I have rarely found one that goes all the way to zero ohms. Still, it usually doesn't matter, especially in a dimmer. They are fairly crude devices that don't get very far off the target, even with a 10% error (compared to the math).

    Don't get microscopic with this. You'll run yourself crazy.
    If you want 0.0 ohms to 1.00 million, you have to buy a, "precision" potentiometer.
     
    atlantis43 likes this.
  11. inwo

    Well-Known Member

    Nov 7, 2013
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    Try with pot disconnected. Maybe something else is afoot.
     
  12. bertus

    Administrator

    Apr 5, 2008
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