Suddenly right channel stopped working, could it be a fuse?

I doubt it is a fuse, but it could be 100 different issues. This is not a DIY repair. If you would like to inquire about repairing your Marantz, please visit my website at audioserviceclinic.com. You may contact me there,

Hi, before going to the repair shop, you might save yourself some expense by making the following checks. More often than not the problem is a simple one. Be methodical in carrying out the checks.
1. SWAP YOUR SPEAKERS OVER. this will eliminate the possibility that one of them is faulty
2. CHECK THE SPEAKER LEADS. Make sure they are not shorting at the terminals on your amp and also at the back of your speakers.
3.CHECK THAT THE PROBLEM EXISTS ON ALL SOURCE INPUTS. For example you may have a faulty input lead on one of your inputs, lets say aux, try switching to CD input and see if the problem still exists. If not its a faulty input lead on the aux input.
4.THIS AMP CAN DRIVE 4 SPEAKERS USUALY REFFERED TO AS, A and B. If you are only driving 2 speakers say from the A output, try swapping the cables to the B output. Also try switching between the A and B setting on the front of the amp to eliminate the possibility of the selector switch being dirty, (do this with the amp on and a signal being played, if it is the switch the missing channel will intermitently be heard) sometimes this will rectify the problem but if not the pot will need cleaning with a contact spray.
Good luck.