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Need Some Help. Bizarre Volume Knob Behavior

Discussion in 'Tele-Technical' started by yeatzee, Oct 22, 2020.

  1. yeatzee

    yeatzee Tele-Meister

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    Long story short I've got a Fender CS Tele Thinline, I'm the second owner. When I got the guitar the volume knob when rolled back would get crackly at times, and when rolled way down or all the way off and was bumped it would suddenly get full volume. Bizarre. I tried cleaning with deoxit on several different occasions and nothing it just got seemingly worse and worse so I bought new mojo pots to replace it with. Just finished wiring it up and the volume works as you'd expect from say 10 - 1.5, then when it is to the point of almost being inaudible if I keep turning it suddenly it jumps to full volume. For the rest of the pots range it has left it stays at full volume but if I turn the knob all the way to where it hits the rotation limit it's intermittent in and out. There's also an additional hum when the knob is past 1 and jumps back to full volume which isn't present when it's on 10.

    I hooked up the pot the same way the factory one was so I'm perplexed. If it didn't work at all ok that's fine I messed up the soldering and I can redo that but here I have no idea what to do.

    Below is a recording starting with the guitar at full volume and slowly turning down. You'll hear it be almost silent then jump to full volume and I went back and forth a couple times. Then you'll hear the crackle when I reach the limit of the pots rotation. After that I turn on a RAT and show how at full volume it's regular noise and then when I roll back and hit the point where it goes back to full volume after being almost silent there's a loud hum that's not present on 10.





    Any help I can get would be much appreciated! This was the stock wiring:

    [​IMG]


    The only change I made was cutting the wire seen going above the pot in half since fender for some reason used one single wire to go from the tone pot through the volume pot to the switch meaning I couldn't remove the pot without snipping the wire or desoldering it from the tone pot and removing it's cloth shield on the side inbetween the tone and volume pots.
     
  2. kbold

    kbold Tele-Afflicted Silver Supporter

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    The upper pot lug looks like a dry joint. Try redoing that joint.
    Also, the capacitor casing looks cracked at the upper leg - I would also replace cap.
     
    Laren and tubedude like this.
  3. yeatzee

    yeatzee Tele-Meister

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    That's all the stock wiring, not a photo of my after with the new pot. Just showing what it looked like. The pot works perfectly normal from 10 to almost off, it's the last 5% that's not working right. I don't think either of those would cause that behavior, right?
     
  4. viking

    viking Friend of Leo's

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    Im amazed that the CS are just as good as me , when it comes to make hot spots on the insulation...!

    Carry on....
     
  5. ale.istotle

    ale.istotle Tele-Holic Silver Supporter

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    May help to see the whole circuit. From what you are describing it sounds like a bad pot. Specifically it sounds like the wiper disengages from the resistor film at the grounded end of the film. I know you just replaced the pot, but is it possible you had to heat the pot case a long time to get flow? That maybe could warp or damage the resistor?
    You could desolder the pot and test resistivity through it's full motion if you have a multimeter to see if the pot is working correctly.
     
  6. ale.istotle

    ale.istotle Tele-Holic Silver Supporter

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    I had another thought. (found this pic on search engine and marked it) The center tap is your output. Blue area of wiper contacts blue area of pc board ring. The red circled part is the point of the wiper - it contacts the red part of the resistor film. If you push past the rotational stop maybe you are forcing the wiper to move past the resistor onto the center tap (teal), pushing it back to full volume? I'm not sure which part is the stop, but if it's part of the poly wiper mount, maybe it got softened when you soldered to the case.


    upload_2020-10-22_14-10-11.png
     
  7. yeatzee

    yeatzee Tele-Meister

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    No hiding with white cloth wire! lol

    I mean anything is possible, but I was not on it for long. I've done far longer stints when upgrading my Les Paul and that had no damage or issues. I've got a multimeter so I could definitely do that, do you have any instructions on what I need to do and what I need to set it to? I'd be happy to check after work.

    Interesting, I guess that would make some sense. I've never heard of that before but I could see that causing this sort of issue. I'm guessing I just need a whole new pot and it's not salvageable. Thankfully I bought two, just don't want to jack up the second!
     
  8. ale.istotle

    ale.istotle Tele-Holic Silver Supporter

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    I think you can test the installed pot as-is now that i think about it. set your meter in the megaohm range. Plug a cable into the guitar. On the other end of the cable put one lead on center, one on the shaft. Resistance should Increase as you rotate toward ground. If it drops out to zero again as you get close to zero on the pot, it's probably a fault in the pot.
     
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