i was using my iMac last week, the screen went pixelated and hashed and none responsive. I switched it off and on and it happened again after about a minute. Since then I’ve not been able to get past the boot screen. It gets about 2/3rds along the progress bar and stops. I can’t get into the recovery mode or diagnostic menu. I can choose the boot menu for boot camp but it crashes out when loading windows. Tried using a usb stick to recover and reinstall but still can’t get past the boot screen. Model is the 2012 iMac. Apple reseller says it’s a vintage model so no parts but could be logic or graphics card. My question is, is this worth trying to fix and anyone got an idea about what it might be?