If your HDMI monitor setting is set to yes, be sure HDMI input is set to "---"
Have you tried connecting the TV with different cables to component video out? Be sure to set HDMI monitor video setting to no and component input to "---".
I know you want to use the HDMI connection but we're narrowing things down.
At this point I must suggest you forget those thoughts about taking a blow torch to it. Just say blow....I mean NO.
If you still get nothing, swallow your pride and call Onkyo tech support, or post a thread in the Amps section, then I'll swallow my pride when they tell you how to fix it on the first reply.