Home Forums GuitarPCB Build Support Mastodon Fuzz not working as expected

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  • #9757
    est
    Participant

    Hello everyone,

    first of all this is my first guitar pedal build and I’m new to soldering/desoldering so some parts are really awful and may need some enhancement but for this first build I’m first trying to make this work, even if not perfectly.

    My first problem is when not mounted in the enclosure:

    • in bypass mode: the signal goes to output in ‘clean’ but volume pot has an effect -> I need to set it to minimal to have maximum volume. I find it weird, I thought bypass was not influenced by anything. I verified my circuit and can’t find what’s wrong
    • once activated: it seems (I still need to verify each pot) to work as expected but with ‘cracks’
    • activated but with no signal: the pedal generates quite a bit of noise

    If I mount in the enclosure the 3PDT and OUT jack, it still works as not mounted. Once I mount the IN jack the behaviour change to:

    • bypass mode works as expected, the volume pot has no effect
    • no sound at all when effect activated.

    Some photos (not sure they can help):

    Any help would be appreciated.

    #9758
    Cybercow
    Moderator

    Can we also see a good, clear, close-up photo of the component side of the PCB? Are the transistors socketed – or soldered directly to the PCB?

    Also, double-check the polarity of the electrolytic (tantalum) caps, make sure the In and Out connections on the main PCB are connected correctly – one of the most common mistakes is connecting the “T” point to ground.

    And finally – double-check the wiring against the wiring guide in the build document.

    #9760
    est
    Participant

    Some photos of the component side

    Transistors are soldered directly on the board.

    The tantalum capacitors are the 47uF ones, C3 and C4. I verified their polarity are good: the leg marked + on the cap in connected to the + socket.

    I was checking the IN/OUT connections and I think I have found one problem: the OUT is inversed -> I think I stupidly follow the ‘wiring board’ schema of https://guitarpcb.com/wp-content/uploads/2018/06/BD_Mastodon.pdf instead of the board schema and they have the OUT inversed. I’ll change those and see what happens.

     

    #9761
    est
    Participant

    Changing the OUT connectivity makes the bypass worked as expected (no vol pot influence) but now I have no sound when pedal switched on.

    I’ll re-check all the wiring schema.

    #9762
    est
    Participant

    Still no sound out. Looking at the board it seems that my multiple soldering and desoldering damaged my OUT T socket. Following the path on the PCB I tried to connect the (now broken) cable on the OUT T directly to the output of the vol pot and this way I have sound ๐Ÿ™‚

    I think I will need to make a direct connection between 3PDT leg 7 and output of the volume pot to solve my problem.

    #9763
    Barry
    Keymaster

    That is an appropriate fix and glad you got it working. On a side note we avoid tantalum capacitors in all builds. If you would have reversed the orientation and applied power there could have been much more troubleshooting.

    #9765
    Cybercow
    Moderator

    est – Yup; that’ll do it. Glad you were able to sort it out.

    #9818
    est
    Participant
    That is an appropriate fix and glad you got it working. On a side note we avoid tantalum capacitors in all builds. If you would have reversed the orientation and applied power there could have been much more troubleshooting.

    Good to know. That was those I found at musikding.de, but maybe I didn’t search enough to found another type.

    est โ€“ Yup; thatโ€™ll do it. Glad you were able to sort it out.

    I’m quite near, this direct wiring worked but when putting it all together in the enclosure it starts failing again. I still need to check it all again.

    I think I’ll order the remaining parts so I can do the final mount inside the enclosure. I don’t think it’ll be before several weeks. I’ll come back here if I’m still blocked.

    Thanks for your help.

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    #9819
    Barry
    Keymaster

    Iโ€™m quite near, this direct wiring worked but when putting it all together in the enclosure it starts failing again. I still need to check it all again.

    This is an excellent learning experience as well. In regards to the “wire dressing”.

    I would suggest that there is more wire than needed. When you try to fit everything in the enclosure there may be stress involved causing an issue. Check out our Combo Build guide on the Guides Page for some excellent ideas. Perhaps reflow all on and off board wiring.

    #12548
    est
    Participant

    sorry to resurrect this old post, but what do you mean by

    On a side note we avoid tantalum capacitors in all builds. If you would have reversed the orientation and applied power there could have been much more troubleshooting.

    what do you recommend to use? At musikding I see https://www.musikding.de/Capacitors

    • film capacitors but seems for high voltage
    • ceramik capacitors but none more than 1 uF
    • silver mica but only 82-1000 pF
    • electrolytic capacitors in for of “standard”, “jamicon”, “bipolar”… “nichicon”, “low impedance”
    • tantalum but not recommended then
    • high voltage, not concerned

    by elimination, I’m left with the electrolytic standard ones I think.

     

    After this failed mastodon first try, I plan to start over with breadboarding some plans from guitarpcb and others. I hope to experiment and better understand how it works, before buying PCB when happy with the result ๐Ÿ™‚

    #12551
    Barry
    Keymaster

    The boards are designed for standard electrolytic since it is not in the audio path. They are affordable and do the job with no effect on sound. While you can use them in the audio path we typically avoid that.

    That said tantalum caps are actually electrolytic. The thing about tantalum quirks that have been written about like exploding and catching fire, while unlikely in a pedal because of the limited power available from the power supplies if you use the wrong supply or install it backwards it could be a problem.

    Therefore we suggest standard electrolytic but you could use either.

    Also always socket transistors.

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