two nights ago i woke up to hear my imac with a black screen and a fan running very loudly. i waited 45 mins and nothing happened so i forcibly powered it off with the power button. Now it doesn't turn back on. I hear the optical drive click but then nothing, no display turn on no chime. did apple try to push a firmware update monday night for the 27" 2011 imac as thats the only other time i've heard the fans run like that. My 2010 macbook pro just died due to a faulty HD-> motherboard cable, so replaced it with a Touchbar MacBook Pro (loving it) but can't afford to replace a desktop as well. any suggestions as to what might be wrong with the computer?