Repair question for Audio Note CD-2

I'm hoping someone with some tech knowledge can help, since I have no expertise in this area. My player has been losing output in the right channel. It's been gradual, but now there's a severe imbalance. I've changed tubes, so it's not that. It still has a very sweet sound.

I'm wondering if someone could tell me (your best guess) what the most likely source of trouble is, and some sort of ballpark figure as to repair cost.

Thanks in advance.