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Volume pot head-scratcher

Discussion in 'Tele-Technical' started by Collin D Plonker, Feb 27, 2021.

  1. Collin D Plonker

    Collin D Plonker Tele-Afflicted

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    Here's a weird one. I have Lindy Fralin P90s in my new build. When I turn the volume down, it drops incredibly fast right away. 9 is significantly lower than 10, and it's not usable past 7. It's totally off by 2. This happens on both pickups regardless of where the tone is set.

    It's wired in the modern Gibson style with (4) 500k audio taper pots. The caps are .0033uF.

    The pots are TAOT CTS, a custom built pot for The Art of Tone. I have used them before with good results..

    The low value of the caps is intentional. I never turn the tone way down (who does? It's not usable like that). I get a natural tone sweep this way, with all positions useable.

    I've wired countless guitars, so I didn't wire it incorrectly. I used 500k per Fralin. I think 250k would be a little dark.

    Any wisdom to be revealed?
     
  2. Wayne Alexander

    Wayne Alexander Friend of Leo's Silver Supporter

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    If you haven't made other wiring mistakes, sounds to me like you have linear taper pots not audio taper.
     
  3. Collin D Plonker

    Collin D Plonker Tele-Afflicted

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    I was suspicious of that, as well, but these pots are supposed to be audio, and the numbers look right.
     
  4. YYZman

    YYZman TDPRI Member Silver Supporter

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    I went through this recently on 2 of my guitars.

    The first, the volume pot itself had gone bad, and gave the same drop once it was out of the guitar and on the bench. Replaced it, all is well.

    The second, the 5 way blade switch in the Strat failed. As in one of the contact discs came loose, and would not move through its full range.

    This is the second Oak Grigsby blade switch that has failed recently; both purchased in the last year and they have never left the house since being installed.
     
  5. SRHmusic

    SRHmusic Tele-Holic Silver Supporter

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    Wired the outer lugs backwards, by chance? Or a reverse taper pot? The taper will be the other way round. (I haven't calculated out what that would do, but just a thought.)
     
    Last edited: Feb 28, 2021
  6. Collin D Plonker

    Collin D Plonker Tele-Afflicted

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    No and no.
     
  7. 2HBStrat

    2HBStrat Tele-Afflicted

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    I've had good luck with Mojotone pots!
     
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  8. kbold

    kbold Friend of Leo's

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    Sounds like incorrect pot taper.
    Time to get out the multimeter and do some measurements (at 0%, 50% and 100% travel)
     
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  9. Digital Larry

    Digital Larry Friend of Leo's

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    A linear pot should drop off more gradually. 50% is only -6 dB.
     
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  10. Collin D Plonker

    Collin D Plonker Tele-Afflicted

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    It's my understanding a linear pot would be quiet on the low end and get loud at 2. Mine is only loud at 10.

    I ordered some vintage taper pots. I guess I will try something different and see how it shakes out.
     
  11. NoTeleBob

    NoTeleBob Tele-Holic

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    Post some DCR measurements of the pot out of circuit at 1,2,3...9,10.

    Any chance there's a stay solder filament somewhere or a wire end poking into something it should not be? Perhaps a cold solder joint?
     
  12. KyAnne

    KyAnne Tele-Afflicted

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    You have the wrong pot taper. Period.
     
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  13. AJBaker

    AJBaker Friend of Leo's

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    It's defiantly not linear, that's the exact opposite of what you describe. On linear pots, 7 is almost as loud as 10, and everything drops off quickly after 5.

    To me it sounds like you have a steep audio taper.

    If you can, take some measurements:

    First, measure the outside two lugs. It should be about 500k.

    Next, turn the pot to 50% of the sweep, and measure left lug to middle lug, and then right lug to middle lug.


    If it's linear taper, you'll measure 250k and 250k.

    If it's a 20% audio taper (my favourite for volume, commonly found in alpha pots and some CTS) you'll measure 100k and 400k.

    If it's a steeper 10% audio taper (commonly found on CTS), you'll measure 50k and 450k. (I like this value for the tone control. For volume control it behaves a bit like what you described.)

    If it's a rare 5% audio taper (I once measured this on a Gibson branded CTS pot), you'll measure 25k and 475k.


    It sounds to me like you want a flatter taper. My advice is to find out what you have, then get a 10% higher taper (if you have 10%, go for 20% for example).

    There are also some vintage style 30% tapers, but I wouldn't recommend ordering from a place called crazyparts. I once got some of those pots and they turned out to be normal 20% taper.
     
    Last edited: Feb 28, 2021
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  14. bender66

    bender66 Poster Extraordinaire

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    I'm reading some confusing info in here.

    It sounds to me like he has audio taper pots. They're working as they're supposed to. I'm not a fan of the sudden drop off. Players that can pull swells (I wish) love 'em.

    I like linear, which I put in anything modded by me for me. I like a consistent roll off from 10-1.

    Couldnt upload just the chart, so heres the link.
    https://eepower.com/resistor-guide/resistor-types/potentiometer-taper/
     
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  15. Geo

    Geo Poster Extraordinaire

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    Could be the internal contact ring isn't making good contact. Could be salt buildup on the wiper
    from sweat, other corrosion or loss of tension on the wiper ring. The ring be cleaned and re-tentioned.
    Sometimes just a good contact cleaner will do instead of disassembling the pot.
    If dissembling, sometimes it can be done without having to unsoldering the wires.

     
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