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Discussion in 'General Electronics Discussion' started by reelingenious, Oct 26, 2017.

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  1. reelingenious

    reelingenious

    1
    0
    Oct 26, 2017
    I have recently rewired my guitar as per the Rickenbacker schematic. The Pickups are TV Jones, and after seeing this same schematic they recommended 500k log pots all round. Now I'm quite happy with the tone as I wanted "top end", hence the 500's I suppose. But the Mixer/blend pot is not very "gradual" and the softer neck PU gets blended in very late in the rotation of the pot, i.e., about the last 5%. Is this a pot value and or capacitor issue. I can follow a diagram, solder and understand some, but am basically an electronic novice!
     

    Attached Files:

  2. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    There are two types of potentiometer 'laws' - linear and logarithmic.

    For audio purposes (volume) it is common to use the logarithmic law versions - if you fit a linear version you find the problem you're experiencing i.e. 'everything happens at one end'.

    In tone control circuits the opposite happens - you need linear, not log.

    Change the pot to the right 'law' and all will be well.
     
  3. 73's de Edd

    73's de Edd

    3,050
    1,288
    Aug 21, 2015
    Sir reelingenious . . . . .

    Since you only have 2 connections, did you replicate the connections that were made into the old pot ?
    Notice that the center connection is being the rotor . . . ..movable contact within the pot.
    Either of the side connections are being the extreme connections of the resistor element.
    Also do note that you are only making two wired connections into the pot.
    There is being a 100% chance that you got the wire going to the center rotor CORRECT.

    The other wire connection will go to one of the end connections of the pot.
    If you choose the WRONG end to put it on the, the quick resistance change that you mention as
    currently experiencing, may be at the full CCW position of the knob. (Whereas it should be at the
    full CW position.

    Try the connection alternatively at both ends and evaluate to see, which gives the desired
    results.

    One way will give you a s. .. l . . . o . . . .w and gradual mixing transition until you get
    near the center of the pot, then a much faster change.
    The other way would have that effect at the OPPOSITE position of the pots rotation.

    I just don't know whether the pot is being at its min or max knob position . . .when expecting
    max CW for maximum bass mix in.

    Otherwise you go to the other option of using a linear pot which mixes in, all in accordance
    to the percentage of its rotation that you have the pot set to.

    BUT then, you wouldn't get that gradual / fine tunable adjustment, at one end of its range that a
    conventional audio log pot would achieve, if being wired in to the correct end terminal.

    Study below . . .
    Take the full left line referencing and mulltiply by 5 to agree with your 500K pots resistance
    Take the bottom line referencing and relate it to the position that your rotor is resting on the
    pots peripheral resistance element.
    Compare the resistance differences experienced when using the BLUE audio log pot and the BLACK
    linear pot.
    The micro adjustment permitted by the LOG unit becomes readily aparrent . . . . or its adverse
    affect if it is wired in backwards.
    ( If a radio had its volume control (LOG) wired in backwards, it would turn on and be as loud as hell . . .
    and then slowly decrease in volume . . . as you turned the knob further to the right )


    POTTY TRAINING . . . . .REFERENCING . . . . .

    [​IMG]


    Little Eddie Ricketybacker Gee-tar info . . . . . .

    "
    Volume potentiometers have also remained a standard 250K log type. Tone and mixer controls have, however, experienced a change in more recent years. These were originally 500K log type. They have now been changed to the same value as volume pots (250K log). Some of the re-issue guitars have the original value in these positions, others do not. "

    73's de Edd
     
    Last edited by a moderator: Nov 1, 2017
    FuZZ1L0G1C likes this.
  4. FuZZ1L0G1C

    FuZZ1L0G1C

    368
    117
    Mar 25, 2014
    "potty training" ... :)
     
    CDRIVE likes this.
  5. Audioguru

    Audioguru

    3,085
    692
    Sep 24, 2016
    I think the pots are shown connected backwards so I fixed the schematic.
    The Mixer pot should be linear.
    The capacitor values should be reduced to match the increased value of the pots for the same cutoff frequencies as the original.
     

    Attached Files:

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