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Thread: Chained pots have short or something

  1. #1

    Chained pots have short or something

    Hi! I am trying to wire up these 33 pots. They are in a chain of 16 and a chain of 17 currently. I tested them before screwing them into this enclosure and I was NOT getting a short circuit between the RIGHT and the LEFT post on any given pot. I was also getting a 0-100k ohm reading between the left and the middle post of any given pot on the two chains.

    Once I screwed them in, however, I re-tested them and was getting a closed circuit between the left and right posts on any pot - but seemingly randomly. This was true of both chains. Then I tested the resistance. On one of the two chains I am getting weird readings like 6k ohms between left and right posts and on the other chain I am getting 1 million ohms.

    It's a alumnium enclosure and non-conductive. I really don't understand how this is happening and at this point I'm pretty worried I just did a few hours work stringing these up just to waste a huge amount of time.

    Any insights or suggestions would be GREATLY appreicated. Thanks in advance!

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  2. #2
    Senior Member manicksan's Avatar
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    even if the aluminum is painted and by the looks of it you have soldered they all on the "front" side of the pot which could make sharp points
    then the paint could be scraped off enough to make connections

  3. #3
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    I would disconnect a line of pots until I found the short then disconnect each pot in that line. the fact that you have soldered your wires into the wiper track holes rather than on the tabs make me think you have a few blobs of solder shorting out to the case or you have some how damaged the wiper track in a few of the pots ? but I would bet its a blob of solder shorting to your case.

  4. #4
    That makes so much sense. You always pop up with the answer! Thanks! I guess Iíll have to paint it?

  5. #5
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    Parallel resistances on your pots

    Quote Originally Posted by Tombot7 View Post
    Hi! I am trying to wire up these 33 pots. They are in a chain of 16 and a chain of 17 currently.
    [snipped]
    Any insights or suggestions would be GREATLY appreicated. Thanks in advance!
    @Tombot7:

    If/when all of the pots are correctly wired, then all of the full resistances of each of the pots (presumed to be 100k ohms each) would be in parallel when measuring across any pot (LEFT to RIGHT, as you describe). Because they are all the same resistance value, the math is greatly simplified for your case. With this in mind, you would expect the resulting resistance for the 16-pot chain to be 100k divided by 16, or about 6.25K ohms. Likewise, for the 17-pot chain, the expected resulting resistance would be 100k divided by 17, or about 5.882k ohms.

    Now, if you measure infinite resistance (>= 1M ohms) at any individual pot, then you should check your soldering at that specific pot. Very likely, one or both of the wires at that pot are not well connected, so they are not actually part of the resulting resistance of the total chain.

    Hope that helps !!

    Mark J Culross
    KD5RXT
    Last edited by kd5rxt-mark; 12-24-2021 at 12:52 AM. Reason: fix typos

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