Hi. First post so don't beat me up too much. My mid 2010 5.1, 4 core running 10.11 El Capitan has developed a constantly flashing power light. It won't boot. Fires up with fans & drives kicking in, but after a few seconds the power light flashes & that's your lot. I'm sure this has been covered many times in the past, but I've never seen a resolution on any other forum. Thinking it was a ram issue, I swapped the ram sticks around until it seemed that ram slot No2 was at fault. I then stuck my 3, 8 gig sticks of Kingston ram in slots 1,3, & 4 & all was fine again. Fired it up a week later & the flashing power light is back, but this time no amount of ram configuration works using 1,2, or all 3 ram sticks. I've unplugged stuff (including the graphics card)& that type of thing but to no avail. Is it likely all 3 sticks of ram have failed?, or is there something more sinister going on?