Troubleshooting A DIY Guitar Pedal That Doesn’t Work
It can be very disheartening for your new DIY guitar effects pedal not to work once you’ve finished building it and plugged it in for the first time.
The smallest error during any phase of your build can mean that the pedal doesn’t work correctly, or at all. If you’re a complete beginner, there are likely to be a few different mistakes but as you progress and advance your skills, you’ll get used to error checking your own work.
Before putting any circuit in an enclosure, you should test it to make sure it works correctly. This will save you a huge amount of time later on as it will help drastically cut down the list of potential issues.
Pedal Is Completely Dead
If your DIY guitar effects pedal simply doesn’t work at all, there are a few checks you should make as they will potentially highlight the issue just by inspecting your work.
Check Components Are In The Correct Place
Revisit your documentation to make sure all of the correct components are in the correct locations on your PCB.
When working on circuits that contain lots of parts, it’s very easy to accidentally put the wrong item in the wrong place.
For any items in the wrong place, simply desolder them and reattach them to the correct spots on the board.
Check Component Orientated
Some components are polarised and the way they’re orientated in your circuit will make a huge difference. The components to check for orientation are:
Diodes – Make sure the end with the band is pointing to the negative terminal of the PCB.
Electrolytic Capacitors – Make sure the side with the negative stripe is pointing to the negative terminal of the PCB.
Integrated Circuits – Make sure the notch at the end of the IC is aligned correctly with the diagram on the PCB.
Transistors – Your PCB should contain the necessary notation to tell you where the Collector (C), Base (B), Emitter (E), Drain (D), Gate (G) and Source (S) pads are. It’s then a case of searching for your transistors datasheet online to find out which pin of the transistor is which.
If any of these components are mounted incorrectly, desolder them and remount them in the correct orientation.
Check Solder Connections
Take a look at all of your solder joints to make sure there are no gaps, cavities of loose connections.
If any of these joints look like they could be providing a poor connection, add a bit more solder to improve the joint.
If you’re resoldering a germanium component, try not to apply too much heat otherwise this will potentially damage the part.
Bypass Sound Only
If your DIY effects pedal allows for your guitar’s signal to pass through when it’s switched off, it’s possible that your switch is wired incorrectly or broken.
If you’ve checked the switch and all seems to be working correctly, it could be that your board is dead.
Strange Humming Sound
A strange unexpected humming sound from your pedal could relate to one of two issues:
- AC Power Issues
- Grounding Issues
AC Power Issues
If you are using a dedicated power supply for your pedal, it’s possible that it’s a faulty plug. Try using a different power supply or a battery (if possible).
If you don’t use AC power (power from a mains adapter), the humming is most likely a grounding issue.
To fix this, check for poor ground wiring connections. Are all ground wires connected to the same point? If not, rewire the grounding of the pedal.
Strange Hissing Sound Or Unexpected Noise
Noisy and hissy sounds are common issues with DIY effects pedals. There are lots of causes for this but the main culprits are:
Transistors & IC’s – Swap these out to use new components. If you’ve used sockets for these components, it should be a very quick fix. If you haven’t used sockets, I’d strongly recommend buying some for future builds.
Poor Solder Joints – If your solder connections are poor, simply reflow the joints and improve the joints.
Poor Contacts – It could be that you have a noisy toggle/foot switch or potentiometer. You can remedy this with switch cleaner.
Unexpected Fuzzy Sound That Slowly Fades Away
The main cause of an unexpected fuzzy/gated sound that slowly fades away is usually a biasing issue.
It could be that your transistors are orientated incorrectly and the best way to fix this is to find the datasheet for your specific transistor (note that some manufacturers create the same transistor and use different orientations for the pins) and realign the pins on your board.
Picking Up Radio Interference
If your working on a DIY high gain pedal like a distortion or fuzz, you may notice some radio interference when the pedal is engaged. This comes down to shielding issues.
Correctly shielding your pedal will prevent the radio waves from actually entering your circuit. The best way to shield your pedal is to use a metal case. If you can’t use a metal case, line the inside of your case with a metal foil.
Pedal Died When Mounted In Enclosure
If your DIY effects pedal worked fine before mounting it in the enclosure, we can narrow this issue down to one of the below issues:
Incorrectly Wired Hardware
This is very easy to do if you rewired the hardware between testing it and adding everything to the enclosure to improve cable management.
Simply go through all of your wires to make sure you have no loose connections and that all wires are actually going to the correct places.
Adding your circuit and hardware into a metal enclosure can be a tight fit and if any of your components accidentally touch the case, it can cause a short.
The best thing to do to remedy this is to check your input jacks and cables to ensure they aren’t touching the enclosure.
If a small enclosure prevents you from making the necessary layout changes, you could use a piece of non-conductive material to block the path. This could be a small piece of foam or a piece of plastic.
If you can think of any other DIY guitar pedal troubleshooting issues that I’ve missed from this list or would like help diagnosing a different issue, please let me know.