Home Forums GuitarPCB Build Support Swah with no effects

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    I’m not new to pedal building but I’m new to this forum.

    I am trying to build the swah pedal that I have bought from the musikdinge store. I have finished all the soldering of the components and have connected all the wires. However, I cannot get the wah effect when I try the pedal with my guitar and amp. I get a clean sound both with true by pass and when I switch to the wah effect. I have already checked that the input goes through the circuit only when I switch to the wah effect ( I press the 3DPT).

    thank for the help.

    Here are a few pictures of the pedal.



    thank for your answer.

    i did what you suggested but now it doesn’t work at all (no TB no effect).

    the lug you labeled as TIP is connected at the “small connector” the “mic” one, the other one is to the “long” (the positive) are you sure the “mic” should go to the input of the board?



    If I understand correctly you get clean signal in both bypass and effects position of the 3PDT? If that’s the case just swap your wires back on the socket end not the pcb end it’s much easier to remove and resolder on the socket lugs

    The most recent problems with this circuit have been an incorrect trimmer value or a D9 series Russian germanium diode where some have the stripe on the anode + side

    Check your trimmer is a 50K code 504 and post voltages on both sides of D3

    It is fairly difficult to see all your component values clearly if you could post a photo of the component side with the wires moved out of the way as much as possible


    yes i get clean signal in both bypass and effect.

    the trimmer is a 50k

    d3 have a misure of .244V (good for a germanium) with the + and – show on the picture:

    the voltage i measured, when i give 9v at the circuit, around d3 is 0.22v and -0.22v (if i invert my multimeters pointers)

    here a more close photo with all components.

    thank for your help.


    With D3 put your black probe to ground and measure the voltage both sides with your red probe it’s just to see what’s going in and what’s going out to Q2 base

    Post voltages on all IC and transistor pins Luigi that may indicate your problem area

    All your component values and orientation look correct


    here my measure (all in V):

    D3) 5.13 on the negative 5.37 on the positive side

    IC1) from 1 to 16 -> 1.30  0  3.74  3.73  4.93  0  4.93  3.72  3.73  4.93  7.46  4.92  3.71  3.71  0  1.21

    IC2) from 1 to 14 -> 3.70  3.70  3.69  7.42  3.62  0  3.69  3.40  3.76  3.69  0  3.68  3.64  5.72

    Q1) CBE -> 7.39  4.34  1.84

    Q2) CBE -> 4.98  5.12  4.62

    Q3) CBE -> 4.98  4.62  4.05

    IC3) Out Ground Input -> 4.99  0  7.34


    Your voltages are confusing me a little Q3 emitter is at 4.05v with only 1.30v and 1.21v going to pins 1 and 16 of IC1

    When you set the trimmer did you turn it in small increments

    Try turning the sensitivity control fully off and using the bias trimmer as a manual sweepable filter to see if you get any wah sound



    yes i did with small increments.

    i try to set SENS to 0 (RES and DECAY to middle) and the trimmer from 0 to max but i still don’t have any effect.

    the measures i did last time was with SENS RES and DECAY to max and the trimmer on the middle.

    new measure with SENS RES DECAY to middle and

    trimmer to 0 :

    IC1) pin1 and 16: 1.32

    Q1) 7.19  4.25  1.79

    Q2) 4.97  5.55  4.97

    Q3) 4.97  4.97  4.35

    D3) 5.55  5.68

    trimmer to max:

    IC1) pin1 and 16: 1.28

    Q1) 7.28  4.28  1.81

    Q2) 4.96  5.55  4.97

    Q3) 4.97  4.96  4.35

    D3) 5.55  5.68

    it looks like that the trimmer makes no big difference. I measure again the trimmer and have (like it should be) a range from 0 to 49.1 Kohm.

    thanks a lot



    Take the LM13700 out of socket and see what voltage you get on pins 1 and 16


    i get on 1 and 16 between 4.72 and 4.95 (moving the trimmer )


    Do you have another to try I’m not 100% sure what voltage you should get with the IC in socket at pins 1 and 16 but I know it’s the current into those pins that drives the filter reading Tonmanns post here it does say it should be low signal


    Hopefully someone with a working circuit can post IC voltages to see if it’s a problem


    Got the voltages from an old post from Petevig

    Yours look to be ok in comparison

    1– 1.34   16– 1.34

    2– 0.69   15– 0.69

    3– 3.56   14– 3.56

    4– 3.58   13– 3.57

    5– 4.75   12– 4.78

    6– 0.00   11– 7.22

    7– 4.75   10– 4.78

    8– 3.56    9– 3.57

    The only difference is your internal diode bias pins 2 and 15 are at 0 whether that would make a difference I don’t know





    if is not the IC, what should it be?


    Could be something as simple as a dry solder joint Luigi

    It’s just a process of elimination

    Are your pins 2 and 15, 0 volts or do you get a small reading


    there are 0 no small reading also if i change the scala of my tester and there aren’t connect to the ground.

    i try to check all solder.




    i check all solder but all should be fine. any new idea?

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