Channel of Yamaha PA dead... Or so I think.

[BeastRenews]

Hello, I'm new to these forums, as well as to the field of music electronics. Recently the channel B on my Yamaha p2100 has died. I say this because the if I use the cord and speaker that was plugged into channel A, the channel B set up does not work, and switching all of channel B's things to channel A works. Also, the PA (last time I used it) seems to have gotten much quieter in its sound output.
I'm looking for someone to put me in the right direction for this problem. I can post pictures and anything else required for me to fix this problem.
Thanks