Hi all, Hoping for some experience or advice here! My MBA refused to turn on in December, called AppleCare but it's out of support, but dropped it into an approved dealer for them to diagnose and repair. They removed and replaced the logic board and the machine came to life, but I was reluctant to spend the £500 and ended up using my MBP for a while. Called up the store a week ago to give them the go-ahead for the repair, and they tried the machine (now with its original logic board) and it booted fine. Collected the machine (very pleased) tested it, and sure enough it booted. However, since getting it home, it only boots some of the time, and when it does, it will turn itself off with no warning. Occasionally on booting I only get half a chime before it turns off again. Any thoughts?