Diagnose 2.1 Speaker Subwoofer Problem?

I picked up this 2.1 Edifier M3300 Speaker set at the Goodwill cheap. The Right RCA connection doesn't produce any sound except for a buzz. The left connection is fine. I check the speakers and they both work when plugged into the Left connection. 

How do I figure out how what is wrong? Could the amp be broken or just the connector?

I don't mind just 1 channel, but if I could fix it, I would like to try. If it's too complicated, I'll just leave it alone.

It is something inside the amplifier/or whatever is generating the signal that is broken. If the case comes off easily, you should look for any obviously blown components. Other than that, there isn't much more you can do without some electrical knowledge.