No output to the speakers from any source

I've owned this AV receiver for 7 years and it has performed flawlessly as part of my Mits Home Theater system. Recently it has been taking several minutes for the input signal to be recognized by the tuner and for the output to the 5 speakers + subwoofer to kick in. Now, I can't get any source to kick in at all. One interesting point; when I tune the FM input to a strong stereo channel and insert headphones in the jack, I can get the sound through the phones if I crank the volume. I've tried every reset possible. Any ideas on next steps to solve this would be helpful. I'm fairly certain there is not a problem with the speakers themselves. I've tried re-securing all of the wiring as well.