Have you tried any basic troubleshooting? First, I'd completely unplug the receiver. Not just power it off. Leave it unplugged for 30 seconds or more. This might reset a glitch.
Next, try a different source, different cables, swapping speaker wire and speakers? Check the speaker wires closely. A loose strand of wire can short and cause data errors. Plus, do you have any headphones? They may work, where the right channel won't. You could at least listen that way, if so. That would also let you know the preamp functions work.
Also, try turning off any DSP Effects/functions. This might bypass a defective digital IC chip, and allow the receiver to at least play an analog source through both channels.
Finally, HiFiEngine has both the manual and service manual. The service manual has instructions on how to run a diagnostic function, that tests for failed sections. It might be worth to join HiFiEngine (it's free) and download the manuals. It can't hurt to at least run the diagnostics routine, to see if it reports a failure? If nothing's found, it might be an issue elsewhere in your system.