A friend of mine has an Onkyo TX-SR706 receiver that had issues where the HDMI ports didn’t work. All he gets through them is green artifacts.
After checking the interwebs, I see that there is a pretty common failure mode in these where the caps on the voltage regulators for the DAC board go bad, and lead to issues. After probing the regulators with my Rigol DS2072A oscilloscope, I found a regulator with a lot of noise on the output indicating a bad decoupling cap.
Put a good cap across it, and viola, all good. Decided to just go through and replace all the voltage regulator decoupling caps since I was in the equipment.
Here is a video.