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Bypass volume pot?

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  • Bypass volume pot?

    I have a keyboard with a bad volume pot that cuts out intermitenly. I am looking to jumper across it to bypass the bad pot from the circuit and could use a little technical assistance.

    The pot has 6 lugs and I want to know which ones to jumper. I have a multi meter and can run test if somebody could help me decipher the results.

    Thanks for the help,

  • #2
    Hi ManRay
    The brand and model of keyboard may help as some one may have a schematic and layout for it.
    However see the attached diagram and maybe can suss it out.
    With 6 terminals I expect it to be stereo with 2 identical channels.
    Two of the terminals should go to ground the only two connected together.
    From the diagram 1 and 1' .
    Two should be connected to the "other end" of the pots resistance and have the signal coming from the sound module.
    From the diagram 3 and 3' .
    Here from 1 to 3 and from 1' to 3' you should be able to measure the pot's or faders resistance.
    Turn the pot/fader to full volume and the wipers (the only 2 terminals left) should measure low resistance between 2 and 3 and 2' and 3'.
    A high resistance reading (twice the pots value)would indicate measuring between 3 and 3'.
    If you now bridge between 2 and 3 and 2' and 3' as long as you always leave the volume at full it should work.
    A new replacement fader would be better !
    Attached Files


    • #3
      Is it a rotary pot, or a slider?

      HAVe you resoldered the thing? Try that first.

      SLiders can be cleaned with sprays. You can also carefully disassemble it, wipe down teh resistive stripe, clean debris from the slider fingers, apply a thin film of Deoxit or MCL, and reassemble.

      Two gang rotaries are hard to do that to, but some will work.

      REad oc's discussion, but also, if the thing sorta works now, then turn the control all the way up and see which pins are shorted together.
      Education is what you're left with after you have forgotten what you have learned.


      • #4
        It is tough to measure the value while it is still installed. The pot (pots) will have a three digit code for the value. 104 is 10,0000 ohms, 105is 100,000. Pots in general follow a fairly predictable progression for value 1, 2.5, 5. The center wire should be the wiper. You are thinking of lifting one wire and putting a fixed resistor between this and the wiper. if the other wiper has a wire attached then you need another resistor to complete the voltage divider for half volume use a 70/30 ratio for these adding up to the value of the pot. Most pots are 1 or two watts but seldom need to be. make sure your resistors don't get hot.
        I think I'd just clean or replace it.