No-load mod for a CTS pot

Discussion in 'Tele-Technical' started by Rob DiStefano, Oct 11, 2008.

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  1. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Why a no-load pot? More than a few reasons but here are my two faves -

    It makes the perfect neck blender pot for a Strat because unlike using pot resistance to null out the neck pickup, a no-load pot is a switch that totally turns off the pup so no signal bleeds to the output.

    There is no question that at higher volumes you'll hear the difference in yer pups' tones with the tone pot removed from the ciruit.

    OK, here's how I mod a CTS pot to no-load ...

    A CTS 250K audio taper split shaft pot, a pair of needle nose pliers for bending the pot tabs open and close, an Xacto knife to start the bending of the pot tabs, a single edge razor blade to remove the part of the carbon resistance strip that'll make the pot no-load.
    [​IMG]

    Using the Xacto knife to get under the pot tab and lift it up just a little bit.
    [​IMG]

    The needle nose prys open the case tabs.
    [​IMG]

    Lift off the metal housing.
    [​IMG]
     
  2. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Lift off the fiber board carbon wiper tray with soldering lugs.
    [​IMG]

    Flip over the tray - there are three solder lugs on the left, where the carbon strip meets the upper lug is where we wanna remove (scrape) off about 1/8" of the carbon.
    [​IMG]

    The single edge razor blade has scraped off about 1/8" of the wiper's copper plating and black carbon film, right near that upper soldering lug.
    [​IMG]

    Reassemble the pot and use the needle nose pliers to push back each of the four case tabs.
    [​IMG]
     
  3. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Get those tabs pushed well pushed down.
    [​IMG]

    All done, and the pot is marked as a no-load.
    [​IMG]
     
  4. bargoedboy

    bargoedboy Tele-Afflicted

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    thanks for that , iv`e never really opened up a pot before . good work .
     
  5. RatherBeFishing

    RatherBeFishing Tele-Afflicted

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    Thanks for the walkthrough and great pics Rob!

    This page also gives instructions for this mod but it mentions doing something to bring the resistance up. Towards the end the author says:

    "Here's another cool trick to bring the resistance values up a bit if you're close.... Carefully take your exacto knife or razor blade and remove some carbon from the inside areas of both the top and bottom areas of the carbon... You aren't scraping the top of the carbon, but the thin sides of the carbon away from the area where the pot connection touches the carbon track..."

    Rob, could you explain what he is doing or even show some pics of it? Do you think this is necessary at all?

    Regards
     
  6. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Removing (scraping off) some of the carbon along an edge of the wiper strip increases the pot's resistance. Ya just need to be careful not to remove any carbon along the wiper's path. I've done it lot's of times to a pot that's needs a boost, say from 234K to 260K.
     
  7. tdowns

    tdowns Former Member

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    Excellent posting Rob. You are da man!!!
     
  8. Jaxson612

    Jaxson612 Tele-Meister

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    Rob,
    Missed this the first time around-great stuff!
     
  9. Mightyaxeman

    Mightyaxeman Tele-Afflicted

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    On my list of projects is a No Load pot blender for my strat. I would have had to ask for this info eventually. Thanks for posting this !!!!
     
  10. red57strat

    red57strat Friend of Leo's

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    Sometimes I can feel the wiper catch where the carbon trace was removed to create the no-load area on the pot.
    To avoid this, I made my most recent no-load pot by painting the area with fingernail polish rather than removing carbon.
    It worked really well though I don't know about the longevity.
     
  11. Cole

    Cole Tele-Meister

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    First off... this a great thread, pics and tutorial Rob! As a lefty using regular CTS lefty pots... a no load pot is now possible. That said... never owning or using a no load pot I think I understand how it works but I need more help understanding the basic no load concept I guess.

    For my next project, I intend to build a partscaster Esquire using a volume & tone 250K pots and a .047 orange cap for starters. No switch. So my question to you is, if I modify the tone pot to a no load by scraping away the carbon as shown in your pics, is this the effect I will achieve: the cap will be engaged and work as it would normally and then when the pot contacts the modified section it will remove the tone pot from the circuit?

    If this is the case... sonically what end does that happen on? When the tone pot is turned full up? Thanks in advance for the clarity.
     
  12. idoru

    idoru Tele-Meister

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    Yep, you got it in one Cole. Turning the pot full up disengages the pot & cap from the circuit. I found it gave a slight output boost & added brightness to my Jazz bass with Hot Stacks - but it didn't make anywhere near as much difference as going from 250K to 500K volume pots.

    c-
     
  13. jivetrain

    jivetrain Tele-Holic

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    i love that little rest that can be felt on fender's no loads when the knob is turned to 10. in fact i'd probably rather buy fender's pots for that reason rather than make my own, but they only offer it in 250k; is there any way to make a no load with that same detent?
     
  14. idoru

    idoru Tele-Meister

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    Here's how to make a detent in a pot (practice on cheap ones!):

    0) Take the pot apart
    1) Make an indent in the pot casing with a punch*
    2) Place the nylon part into the casing, turn it to where you want the detent to be*
    3) Use blu-tack to hold the nylon part in place.
    4) Apply a 40W soldering iron + solder to the indent - for too long, like when you're first trying to get wires soldered to the pot casing.
    5) Use a sharp knife to scrape off the melted nylon from around the indent.
    6) Reassemble the pot.

    * This bit is a little tricky, it's easier to do with the pot in front of you and a multimeter than it is to explain!

    Yes, I discovered this by accident when soldering up a No-Load pot. I lingered slightly too long when soldering the cap, and had a perfectly formed second detent around 7 on the knob.

    c-
     
  15. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    For a lefty, if you wire up a pot "backwards", make the no-load scraping on the other side of the wiper strip, then it'll work as indicated - with the tone pot fully engaged the cap will be out of the circuit and as you turn the pot knob slightly "off" it will introduce the cap into the signal path.
     
  16. tdowns

    tdowns Former Member

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    Here is a Fender no-load pot. I wonder why there is so much missing in the CW area?? This limits the effective sweep of the pot.

    [​IMG]
     
  17. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Terry, are you sure that the "detent patch" is really non-metallic? Looking at the case detent, it looks like the wiper would stop after the detent and bypass the "patch", which would mean the last most blackish area of the wiper on the CW side, by the solder lug, might the be non-metallic "off" area? Just a guess.
     
  18. ChristoMephisto

    ChristoMephisto TDPRI Member

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    Did that no-load mod to a push/pull pot back in the summer. Couldn't get it apart, but its just as easy to fit a knife in there to cut it.
    Now my tone pot acts as a no load and a phase switch for my neck.
    Funny enough, read somewhere the only difference between a balancer and a no-load is the no-load has the clicking feature.
     
  19. tdowns

    tdowns Former Member

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    It is metallic and it's connected to the end of the resistance path. See the illustration below.

    [​IMG]
     
  20. Rob DiStefano

    Rob DiStefano Doctor of Teleocity Vendor Member

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    Ah, now I understand what you meant by "missing in the CW area". I don't get it, either, I'll stick with my CTS no-load mod, cheaper, faster, discretionary, works perfectly. :cool:
     
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