Home Forums GuitarPCB Build Support SWAH troubleshooting (solved)

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    thank you for the Tip with the IC3. But sadly for the ST L78L05 voltage regulator the printed hull on tzhe pcb is OK. The search countinues……




    i uploaded the images of my pcb, I compared it visually to the successful built from Barry, but not did not find anything.Maybe I youst do not see it (R26 is on the back side, cause I played with the value a bit, to test the wahwah function with the trim poti, to verify that the wahwah part works)


    I finally found the error, the TL074 was faulty. I would not have guesses that this is the error. But now it works. For all people reading this while searching for an error. What helped me most was the very old block schematic, which shows what every circuit part does.

    In my case i could exclude the wahwah part as I could wahwah with the trim poti. When knowing what section is faulty the swah is quite fast to test, as only a few parts remain.

    Thank you Barry for your help




    Wonderful!  It is unusual for a TL074 to be defective.  But, stranger things have happened.  Happy to hear all is well now!


    UPDATE with resolution:

    The problem was the germanium 1N34 diode I was supplied were the Russian type where the band marks the anode and not the cathode as standard in the west. Once the diode was reversed, the circuit works as expected.

    I didnt even know this reversed band on the diode was a thing. Im going to update my vendor to let them know, but if these parts are being supplied by vendors of the PCBs then a note in the documentation might save some grief.


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