My workhorse machine is a 2.5 GHz A1260 with 6GB RAM and an SSD swapped in for the optical drive. I love it, scratches and dings and all. I've lost track of how many times I've disassembled it, and it's missing a few screws.

For the last six months or so, the sturdy machine has had intermittent narcolepsy: it goes to sleep on its own, with no provocation, whether plugged into AC power or not. The behaviour started with a dying battery, but I'm running on a brand-new one now.

I haven't cared about the issue so much up to now— it only happened once a day or so, and the computer's brief naps gave me a good excuse to go stretch. But today, it's gone to sleep three times thus far and shut off with no warning twice. It's been plugged into an 85W AC adapter the whole time.

This issue may be similar to Random MacBook Pro shut down, but we never saw a resolution on that.

• Goes to sleep randomly a couple times a day, with ever-increasing frequency
• Loses power, even while plugged into AC with new battery

• Tried at least three batteries, including new battery
• Used multiple 85W power adapters
• Reproduced issue at multiple locations, so it's not the mains power.
• Removed ambient light sensor.
• Installed known-good ambient light sensor.
• Removed sleep sensor.

When it shut off on me today, it was plugged into power (glowing amber) and my battery was at about 80%. Started it back up, ran for about 5 minutes, then shut off again. Since then, it's been working fine. The computer hadn't been running much yet and wasn't warm, so it's not a heat issue.

Today, it started shutting off within 2 minutes of boot. I'm typing this on another machine. Taking it apart now; I'll start swapping components.

It's not the ambient light sensor or the sleep sensor (tested known-good parts on both). I swapped in a new upper case an hour ago, and it hasn't shut off since. I'm crossing my fingers, but not overly-optimistic yet.

Some things just can't be fixed! I hate to say it, but I was forced to give up on this machine and upgrade. We parted out the old machine, so it didn't end up in the dump, but I never did figure out what the problem was.

Sometimes, with the tremendous technical complexity of these machines, you have to put the problem down to something at the board-level. I'm pretty confident replacing the main board would have fixed it (I tried everything else that made sense), but at that point I was better off recycling the machine and upgrading. Thanks for all the help with the issue!