My remote doesn't work on my Denon 2105. Is there a simple way to know if it's the remote or something in the receiver? I tried 3 sets of batteries and don't have a backup remote.

Take the remote into a Denon dealer ?

Find someone nearby with a similar receiver ?

Or... if you have a remote for some other device which can learn IR codes you can see if that remote can see the codes from your remote.