Reformat the HD when Screen isn't working
Hi folks; my iMac 27" from 2011 has a bad graphic card. The screen doesn't stay on for 1 or 2 seconds at the most. I tried hooking another monitor via Mini Display -> HDMI port on the Monitor but unfortunately nothing shows up on the external display (monitor). The Hard Drive is booting and is working ( I know because I can feel the vibration from the HD).
I want to send it to Apple recycling however I want to reformat the HD first (I already have a back up); since screen isn't working I'm thinking I have to physically take out the HD and reformat. Anyone know how can I reformat the internal HD after removal form iMac 27" casing? Any help is greatly appreciated.
iMac 27″, macOS 10.13