Fender Passport Event

[ricach]

I have the Event version of the Passport but its similar to all the Passports. The output on both speakers are very weak. It appears everything on the mixer and preamp side work properly including the master volume, but the most sound that comes out of the speakers is barely a whisper in volume. I'm about to dive in with a meter and schematic, but since both sides are effected I'm guessing it should be easy to track down the problem. My first guess is somewhere in the power supply section not properly powering the power amp, but since its a switching power supply, I don't look forward to troubleshooting that.
Here's a link to the service manual:
https://www.manualslib.com/manual/10...-Passport.html

[Enzo]

I doubt the SMPS is bad. If it were, nothing would work.

I see output of mixer shares an IC at the master volume stage, plus another shared IC as a buffer the stage after. Either could do this. But I also see mute transistors before the master volume stages. If those are stuck on, you signal dies.