So whilst this is a little over my pay grade, I'm giving it a whiz at repairing this beautiful receiver. I found this at a charity shop and decided to pick it up. At first, it would do the thing that's most common for these SX-550s to do, flicker the power light. I managed to fix that issue, but now have another issue that I must admit, I don't quite understand. Once I got this to power up, the left channel was highly distorted, and was quite a bit lower in volume compared to the right channel. I've tested all the different inputs, and it doesn't change no matter the input (including radio.) When testing using the headphone output, it works fine. Both channels sound reasonably great. No distortion, and both are same volume to each other. Now, I am unsure if the outputs for speakers at the back and the headphone use the same circuit, looking at the circuit diagram, it looks like they do but again, I am no expert, just my first repair project on something like this, so I am more than likely wrong on this wrong. Going with that mindset, I was tracing the back of the board as best I could, and to be quite honest, it doesn't look right to me. It looks like there has been some sort of liquid or something spilt as the back of the board looks quite bad, and some of the traces look as if they have been slightly eaten through with something corrosive. (Included some pictures of the back of the board.) I will also add that, it's only I guess the audio side of the board that looks this way. Looking at the opposite end of the board, there is nothing on it, it looks fine. If anyone would be able to shed some light on this for me as to what the issue might be, that would be excellent. Thank you!