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Phat Phuk B internal gain question

Discussion in 'Effects [BG]' started by LowEndWooly, Nov 25, 2018.


  1. LowEndWooly

    LowEndWooly

    Sep 3, 2013
    Indiana
    44784BB5-9FC9-41E5-A0AC-994AEE1B8A92. I’ve had a PPB a few years ago and loved it. I got this one used on here, but the guts seem a little different than I remember. I thought there was a tiny pot inside that could be turned with a screw driver or something.. I opened this one up and it looks like there’s some black covering on part of it. I’m wondering if the gain control is under that? I don’t really know what that is or if it can be removed safely.

    Anyone have any ideas on where the internal gain control is? I don’t want to mess this beautiful pedal up.
     
    zapped777 likes this.
  2. Grahams Groove

    Grahams Groove If it feels heavy, it's heavy. Supporting Member

    Apr 13, 2001
    Boulder, CO
    Did you adjust the pot that looks like a small, 'regular' screw-head? The one in the center on the blue W102...

    I defer to someone else who has built or owned one of these, but that looks to be it. Not sure if this is an earlier or later PPB build...
     
  3. LowEndWooly

    LowEndWooly

    Sep 3, 2013
    Indiana
    I was going to try that one, but I was afraid it would be something else and mess it up. It doesn’t look like what I remember.. I suppose I should know within a quarter turn. I’ll try it.
     
    Grahams Groove likes this.
  4. Grahams Groove

    Grahams Groove If it feels heavy, it's heavy. Supporting Member

    Apr 13, 2001
    Boulder, CO
    No harm if you remember or take a photo of the starting position. You can google that part number and see that those are another version of a potentiometer. It definitely looks different than the one I had in my PPB (which was the square, blue potentiometer with a phillips head). Maybe Matt and his team were using different parts at one point. Does the back panel of the enclosure have a date/signature?
     
  5. Jonny5bass

    Jonny5bass Supporting Member

    May 3, 2011
    Seattle, WA
    The screw on the blue “W 102” is the correct one to change the bias. My first of three had that design.
     
    LowEndWooly likes this.
  6. vivaknoxvegas

    vivaknoxvegas El Duderino Gold Supporting Member

    May 6, 2002
    Knoxville, TN
    LowEndWooly likes this.
  7. JonnyAngle

    JonnyAngle Dropping Acid Pedal Etching .com Supporting Member Commercial User

    Nov 24, 2008
    Maple Grove, MN
    DroppingAcidPedalEtching.com
    This is the correct answer. There’s 2 or 3 different pcbs for this pedal
     
    LowEndWooly likes this.
  8. LowEndWooly

    LowEndWooly

    Sep 3, 2013
    Indiana
    Thanks for the help! I'll try it tonight and report back
     
  9. Crater

    Crater

    Oct 12, 2011
    Dallas, TX area
    The black stuff is called "goop" by pedal nerds. It's basically black epoxy, and it's sometimes applied to boutique pedals' circuitboards either to protect the the builder's intellectual property or to hide the fact that a pedal is a cloned version of a commercial pedal. Don't try to remove it!

    Yes, the blue box with the brass screw is a trim pot, but this appears to be a 10-turn type trim pot. This type allows for finer adjustment. It's NOT a "gain control". Google tells me this fuzz is a two-transistor design with an FET for the first stage that feeds a PNP germanium transistor. Germanium transistors are notoriously inconsistent, so the trim pot is installed so the Ge transistor's bias can be set to the optimal point. Bias is normally adjusted by measuring the voltage between ground and the transistor's collector terminal. Usually the bias point is set to about half the supply voltage or 9/2 or about 4.5 volts. I wouldn't adjust it until you know where to measure the bias voltage.
     
    LowEndWooly likes this.

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