Left channel weak and scratchy?

I have a Pioneer Sx-1080 that I recently purchased on ebay. I bought a pair of JBL E30 to hook up to them. The problem is that most of the time when I turn it on, the left channel is very faint compared to the right and very scratchy and staticy. The right channel sometimes gets scratchy too, but not nearly as often. If I wiggle the volume or balance it will sometimes come on. Even when both seem to be working, the right seems to have more output than the left. I know nothing about electronics so I have no clue what this could be, although I have heard that sometimes contacts need to be cleaned. Could anyone shed some light on this situation for me? And does it sound like an expensive fix? Thanks.
Turn off the unit and turn the volume knob up and down fast a bunch of times. This will clean up the contacts in the volume pot if this is the problem.

I would also recommend leaving the unit on all the time so it can thermally stabilize.
open up the cover and spray some contact cleaner (oh allright... wd-40 might work in a pinch...) on the volume conrol if the first suggestion yields results