Hello, my name is Rusty. I can help you, you came to the right spot. I'm going to ask some questions, and then I will be able to make my diagnosis. If needed, I can help you tear it apart and fix the problem. Let's get started.
I need you to check the headphones, see if you get sound. I also need you to test the percussion, and tell me if you get sound. I also want you to plug the headphones directly into the main output of your keyboard, and tell me if you hear sound out of one ear.
The things we are testing is if the problem is internal or external. Headphones use a different amp system inside Korg than the main outputs. Testing the headphones tells us where the signal is blocked. Testing the main outputs with the headphones tells us if the problem is internal or external.
If you hear sound from the headphones, unplug the headphones so that the main outs are not muted. If you hear sound from the main outs in one ear, check your wiring to your amplifier, and verify that it is on.
Please tell me the results.