Hum in main

[YogaGriot]

Help! EuroPower PMP960
I was doing an equipment check through a single speaker. I hit the fbq button for the first time. It made a loud pop, so I depressed the button immediately. The amp now has a hum in the main and the sliders on the eq sound dirty when I adjust them. So far, I have:
-swapped out cables
-tried different speakers
-restarted amp
-checked each channel
-tried to eq it out

I am able to run the main at low volume and run the channels hot to make the hum less audible.

Any suggestions to eliminate this problem is greatly appreciated! I have a memorial service on Tuesday, 10/25!

PS - I am a novice