How to disable HDMI during boot to keep it powered off?

I had a lightning strike nearby and the hdmi output on my receiver quit working. The component A/V still works so I'm able to get a picture, but the CPU is overheating and shutting down after about 10 minutes. I think if I could disable the HDMI maybe that would stop the overheating? I know with a raspberry pi the HDMI can be disabled at boot by editing rc.local, but I cant find anything similar for enigma 2. I got it working with a fan blowing on the heat sink for now (1/2hr so far). Its an Octagon SF8008 Combo. Any ideas? Thanks in advance

HDMI is working again. I got a fan in there hooked up to the 12v from the switch in the back. Temp on the CPU topped out at 91C. So far so good... Weird stuff that lightning

91C seemed a little high so I made a shroud and got it down to 77C...

... I would still like to disable the HDMI to see if it stops overheating. The fan is noisy.