Harman Kardon HK 610 only playing out of one...

Question

Hi!
Anyone know anything about this amplifier.  Mine has decided to only play out of one speaker on all channels except the CD channel and I've swapped the speakers over already, it's definately not them.  Could it be dust inside?  Will I kill it dead if I even attempt to open it up and have a look?  I don't really want to throw it away and places that I've rung to fix it just tell me to get a new one.
I'd appreciate your thoughts.
Kelly