The wedding isn’t happening until later this afternoon so I have a bit of time right now to help figure this out…
First of all, sorry for the trouble. Secondly, don’t worry…we’ll get this fixed real soon and you’ll have a nice amp to play through. I’m out of state right now so i don’t have an amp in front of me, but we can get started with what i remember.
Thanks so much for the photos. That really helps. The voltages you read seem correct when the amp is plugged in to the wall and the switch is on, but from now on keep it unplugged until we get some more measurements done.
With the meter on the continuity setting (it’s the one that makes a beep when the two probes touch…not the voltage setting) test weather you have continuity between the round pad of P4 and the middle pin on the switch (it should beep if there is continuity). Also check weather you have continuity between either of these points and ground.
Also, check for continuity across the fuse to see if the fuse blew when you saw the fireworks.
Do these tests and let me know what you find.
Good luck.
-brach