Guitar Effects Debugging Page

Please note: This page was updated 8/5/00 and is getting pretty complete. There is some material that is not yet sorted into place. A few links are still just stubs, but it does cover a lot of situations. As always, additions and corrections are welcome.

Assess your personal capabilities
Have the right tools
Getting brand new effects that you've built running for the first time
Geriatric Effects - resuscitating the elderly stompbox
Select the most obvious symptom:
- Has the effect ever worked? That is, is it one you built new or is it one that is either commercial or that used to work OK?
- Mechanical damage - broken case, broken knobs, cracks, crunches, evidence of liquids poured in, etc.
- Completely dead - no sound whether bypassed or not, no indicator lights (if the effect has them), nothing
- Sound only when bypassed, no sound at all in the effects position
- No or very little effect in the sound when the effect is engaged
- "Blatty" or gated sound or sound only when you hit strings hard, or sound only as the note decays away.
- Hum
- Hiss
- Radio interference
- Distortion on effects that are not intended to distort
  Almost always a bias problem. The DC voltage tests, transistor tests, or opamp tests should show this one up.
Testing Transistors in the circuit
If you think you have a dead transistor, try this.
Testing Capacitors
Temporarily unsolder one lead, and measure the resistance with your ohmmeter. It should read open circuit on the highest scale.
Testing Resistors
Easy - measure them; however, the other stuff in the circuit may cause a fake lower reading. To get an accurate measurement, you have to unsolder one lead.
Testing operational amplifiers (op-amps)
Symptoms peculiar to particular types of effect
- Distortion pedals
- Phasers
- Delays of all kinds - flangers, chorus, echos, digital delays, etc.
- Spring reverbs