Sometimes we'll hear from a customer that the FX Loop in their amp isn't working. The signal is weak, the signal cuts in and out, or there may not even be a signal at all.
This is a very uncommon issue and rare that the FX Loop itself is the problem. In this case, you should start by troubleshooting everything in your rig. It's likely that either a pedal you're using, or a cable is the culprit.
However, if you've tried that and you still suspect that your FX Loop isn't passing a signal, here's the way to check to see if it's doing its job:
Take a cable and plug the FX Send directly into the FX Return. Set your instrument up and play as normal.
- If you hear your instrument, then it can be ruled that the FX Loop is working fine and the issue is caused by an external factor.
- If there is no signal, then there might be an issue with the FX Loop.
It is also best to try this with different cables to ensure the problem isn't with the cable.
However, if you have a Mach 3 and have an issue with the FX Loop, there may be a reason for that. More info on that here.