The pedal started out with an over voltage burn out. Two components had burnt out. One of them was the reverse polarity protection diode which was designated on the board. The other was unknown. Following the trace path after the diode that led into an electrolytic, which then ended up at voltage regulator IC, I wasn’t sure what this was used for. After contemplating for some moments I decided to put another diode in this position, thinking at worst I would just blow it up again. The pedal didn’t turn on and thinking about the logic a little more, I knew I needed to simply flip the cathode on the diode that was feeding into the regulator. And just like that, the LED worked. So I went to plug in guitar and amp for testing and no sound came out of the wet or dry outputs. Totally baffled… I outlined my next steps. I ran out of time, because this was at a friends house, so I went to the drawing board on what to do next.
- trace the 9V node and find out if any other parts could have been damaged on that node.
- trace the signal path starting with the 1/4 jacks using an audio probe and see where the guitar signal stops.
After I left my buddy put everything back together and it turned out that replacing the diodes actually did the trick and all the pedal needed was be assembled. This is common for a lot mass produced and digital pedals. The longest portion of troubleshooting was because I was not testing properly. Replacing the diode took 5 minutes, but the remainder of the head scratching took two hours, until I just basically put the enclosure back together.
