Do you fix QSC Power amps?

@warrenreed96485 iFixit doesn’t actually fix things for people. The site is a place for people to learn repair for themselves—the “i” in iFixit is you! For this repair, I’d start by checking Switch Mode Power Supply (SMPS). Reason for is that you have buzzing on all channels which is typically an error with an external ground loop from the input source or teh SMPS.

See if we can narrow it down. Disconnect all the input cables from the amplifier, leave only the speaker outputs and the AC power cable connected. Turn the amp on. If the buzzing completely stops, the amp is functioning normally, and the noise is an issue with an upstream mixer, a damaged audio cable, or a ground loop between your equipment racks.

If the amp still buzzes with nothing connected to the inputs, unplug it and connect it to a complete different outlet/circuit. Faulty dimmer switches, fluorescent lighting, or other failing electrical equipment on the same circuit phase can directly cause a hum into the amps power cord.

If the buzzing persists on a clean circuit with isolated inputs, the SMPS is failing to filter the power. For that you would have to check all the caps on the SMPS to see if those are actually still filtering. Remember to discharge all the caps after you disconnect the power from the SMPS. Those hold a charge reasonably long and can zap you pretty good if not discharged.

Let's see if we find some schematic for this amp to help you further.