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Thread: Faultfinding DIY Pedal Builds

  1. #1
    Overlord of Music DrNomis_44's Avatar
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    Faultfinding DIY Pedal Builds

    Hi Everyone,

    While there seems to be quite a few threads about building DIY pedals in this forum section, I noticed that there isn't a thread about faultfinding them, so, I thought that I would take the initiative and start a thread about faultfinding DIY pedal builds....so here it is.


    Okay, you bought a DIY pedal kit online, assembled it, and for some reason it doesn't work as it's supposed to, so what do you do?, whatever you do, don't give up, because believe it or not, it is quite possible to get a non-functional DIY pedal build working as it's supposed to, all you need to do is go through the fault-finding steps one by one until you discover what's causing the malfunction.

    Most of the time when I build a DIY pedal, I've been pretty lucky and my DIY pedal builds have usually worked first time, but sometimes I do come across a pedal build that doesn't appear to work as it should, here's a procedure that I usually follow to get the pedal working:


    1, First thing I do is give the circuitry of the pedal a good visual inspection, I do this by having a close-up look at all the solder-joints on the circuit board with a X10 Magnifier, sometimes the cause of a malfunction in a DIY pedal build can simply be a cold solder-joint, this is where the solder hasn't properly adhered to either the component lead, or the copper track on the circuit board, or it can be both, it can even be a joint that hasn't been soldered, I'm sure that I've done that at least once ever since I first got interested in Electronics.

    The fix for a cold solder-joint is pretty simple, first I de-solder all the existing solder, then I remove the component, then, using a stanley-knife blade, I scrape the component lead so that it is all silvery and clean all over, this will help the solder to adhere better, next I remove any residual solder from the copper track and gently scrape it so that it is shiny and clean, you can use solder wick to soak up the residual solder, I recommend buying a roll of 3mm Goot Solderwick from your local Jaycar Electronics shop, I find that Goot Solderwick tends to work really well, better still, buy two rolls.

    Once both the component lead and copper track are clean and shiny, put the component back in it's position on the circuit board, making sure that you get polarized components oriented the correct way around, and then re-do the solder-joint, if the solder-joint looks bright and shiny it should be good.

    Another cause of a malfunction in DIY pedal builds could be a broken wire, in that case you simply re-solder the wire connection.

    Or, some part of the circuitry might have inadvertently shorted-out to circuit ground.

    2, Once I'm satisfied that everything looks good after doing my visual inspection, I get my digital multimeter out and use it to measure the DC voltages present in the circuit while it's powered up, if I get any unusual DC voltage readings in any part of the circuitry then that immediately tells me where the fault is most likely to be and I start investigating the cause of the unusual DC voltage readings, sometimes these unusual DC voltage readings can be caused by a faulty component, or, a copper circuit board track that might have a hairline crack/break in it that's very hard to see, in the case of a faulty component most of the time replacing it with a known good one is enough to fix it, in the case of a hairline crack/break in a copper track, bridging it with a short piece if component-lead cuttoff that's soldered in place is enough to fix it.

    I've also come across a faulty 9V battery connector a few times too, replacing it completely with a known good one fixed the non-functional pedal I was working on.

    3, A Component getting abnormally hot is another cause of DIY pedal malfunction, it could be as a result of the component failing, or it could be something related to the component that's failed, so it's always a good idea to check for any components getting abnormally hot (making sure that there are no dangerous voltages present, which is unlikely in a DIY pedal designed to run on 9V DC), sometimes a component will get abnormally hot due to it oscillating at a very high frequency, this can happen in small amplifier circuits.

    4, If I haven't fixed the malfunctioning pedal at this stage I usually take a break from it and come back to it later on with a clear head, this is not only a good idea, it's also important to allow your most powerful faultfinding tool, Deductive Reasoning, to work at it's maximum effectiveness, also, trying to faultfind a malfunctioning DIY pedal build when you're in a bad mood is an exercise in futility, because you're unable to think logically when you're in a bad mood, or upset, so, always try to keep your cool, I'm sure that I've been guilty of loosing my cool when faultfinding a non-functional DIY build on a few occasions, and when I've come back to it with a clear head, the cause of the non-function turned out to be so obvious it was staring me in the face, making me feel like a right goose.

    Faultfinding a malfunctioning piece of electronics is a lot like solving a mystery, make sure you make a note of the symptoms that a malfunctioning DIY pedal is displaying, because the symptoms can be valuable clues to what could be causing the malfunction.


    More info to come so stay tuned.


    Note: All comments/contributions are most welcome.

    Also note that these faultfinding procedures can be used to faultfind malfunctioning electronics in guitars too.
    Last edited by DrNomis_44; 10-10-2017 at 07:56 PM.

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  3. #2
    Member JohnH's Avatar
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    Excellent idea for a thread. I need this info for sure!

  4. #3
    Member Joe3334's Avatar
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    I need this more than anyone, I just started building a pedal earlier today and I've already gooched it, luckily the Chinese seller is giving me a free replacement with all components.

  5. #4
    Member mjg's Avatar
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    One thing I check pretty early on is that I've put the components in the right way - electrolytic capacitors, diodes, LEDS, and transistors.

    Quite often I've had a pedal not work, and the simple solution was that I'd put a transistor in backwards.

  6. #5
    Overlord of Music Fretworn's Avatar
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    Building yourself an audio circuit probe is helpful..
    Current:
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  7. #6
    Overlord of Music Andy40's Avatar
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    Thanks for posting doc
    Build #1 - ST-1 - Completed and upgraded
    Build #2 - LP-1SS - Completed | Co-Winner-May 2016 GOTM | Runner up GOTY 2016
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  8. #7
    Overlord of Music DrNomis_44's Avatar
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    No worries Andy40.


    An Audio probe is definitely a handy piece of test gear to have alongside your soldering iron and multimeter, I need to build myself one or maybe two of them, so when I do build one I'll do a mini-tutorial while I'm at it, a Signal Generator and Oscilloscope are very handy to have as well, you might be able to pic up a decent Scope on eBay for a reasonable price, but an Audio Probe works out cheaper.

  9. #8
    Member JohnH's Avatar
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    That audio probe is a great idea! Will have to make one sometime soon

  10. #9
    Member JohnH's Avatar
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    Quote Originally Posted by Joe3334 View Post
    I need this more than anyone, I just started building a pedal earlier today and I've already gooched it, luckily the Chinese seller is giving me a free replacement with all components.
    Joe, I meant to ask, what did you do to gooch it?

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