Home Forums GuitarPCB Build Support Dr Rock Pot (solved)

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    I just realized that there is very little sweep on the distortion knob.  It goes from zero to to full out distortion on one!  I am thinking that it can be a bad pot, anything else i should consider?  Otherwise the pedal works perfect!!



    David – Which pot are you naming as the “Distortion” pot? And what specific taper and blue of the Gain pot (P1) are you using? It works best if it’s a linear taper. (B500K)

    I’m only guessing that you named the Dr Rock “Gain” pot as “Distortion”.

    Also, what are the voltages at supply, IC1 (all pins) and Q1 (all 3 pins) please? Photos?


    Hello.  Yes I meant gain.  the voltages are as follows:


    1. 155 mv
    2. 4.65 v
    3. 4.42 v
    4. o
    5. 154 mv
    6. 4.65 v
    7. 9.33 v
    8. 17 mv


    d 9.33

    s 1.28

    g 0



    David – and photos please. The closer and clearer the better.

    Also, 4.65 v on pin 2 of the IC does NOT seem right. Perhaps Berry, Wilkie or another moderator will chime in with more experience with this build. The photos could be more revealing too. We’ve no idea what you are seeing otherwise.

    Did I mention the importance of photos? 😉


    Did you use a Linear Taper?

    In some countries A500K and B500K or A & B mean the exact opposite USA uses the common Asia method for labeling A for Log and B for linear but Europe uses the opposite of A for Linear and B for Log.

    In USA per my Build Document B500K means Linear and not Log.

    Log would have the effect you describe as Cybercow mentioned.

    The Taper could be the only problem.




    Check to see if lugs 1 and 3 of P1 are wired to the correct pads.  If they are reversed turning the pot from 0 to 1 would immediately change the resistance to @ 500K.


    I figured it out.  It was a combination of a bad pot, and the my inexperience with drive pedal sweeps. . The Alpha pot was an older version,newer ones are so much smoother and better build qualities.  Oddly enough, hooked up to an ohm meter it seemed fine but not until I tried a new pot was I able to hear the difference.   The casing was loose and the sweep was not smooth.  In addition, the sweep on the pedal is a bit odd to me, I did compare it with an old Japanese Ds-1 and it is exactly the same. Its a really nice and easy pedal to build, I think I will order another one.

    Thanks for your help everyone!!


    Thank you for reporting back and enjoy!

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