MacBook Pro 13 early 2011 repeated unexpected shut down
This machine has had problems for 6 months or so, spontaneous shutdowns and automatic restarts. It's been back to Apple twice: first time a cable change, the second a new logic board. The HD and memory have been changed. SMC has been reset. It's running Yosemite.
After the logic board replacement the symptoms changed: the shutdowns occur apparently at random, sometimes a couple per day, sometimes it will go a week without problems. I could see no pattern in the problem reports - but I'm not an expert at reading them! However now there are problem reports, previously the machine stopped, restarted, and carried on as if nothing had happened.
These are not kernel panics with the falling curtain and multi-language message, the machine just stops and the screen goes dark, then restarts as if from a normal shutdown.
Taking it back to the Mac store is an option but the problem is the intermittency, it could run for days without failing and even Apple can't do much about a fault that doesn't happen to order!
I can't imagine that it's a software problem, but if it's hardware then really it's the logic board again isn't it? I'm at a loss to know what to look at next and I'd appreciate some thoughts from others please.
Keith
MacBook Pro, OS X Yosemite (10.10.2)