17 in Macbook Pro (mid 2010) unexpected shutdown

After digging out the install discs to run the Hardware Test (there has to be an easier way...) I discovered that I couldn't insert the DVD in to my superdrive. Since I used it a couple of weeks ago and there hasn't been any assault on my laptop I considered this extremely odd.

I removed the bottom of the chassis and took a look around, nothing obvious.

I placed the bottom in place and powered back up (no screws installed) and the superdrive worked without a hitch.

<LIGHTBULB>

I powered down, reinstalled the screws (just snug, not tight) and rebooted into the Hardware Test.

HWT reported all is well and after several hours I have not experienced a shutdown.

My best guess is that over-tightening the screws created some sort of glitch that resulted in the erratic behavior.

Your theory is correct.

But now I can replicate the problem reliably, even if I can't yet determine the cause.

Running on A/C power all is well.

If I unplug the power cord things run smoothly for a few minutes, then the screen goes black and the indicator on the front of the chassis activates. The only way that I have discovered to recover is a hard reboot. No amount of key-tickling or power-button pressing will awaken it. (But now I realize I haven't tried closing and opening the clamshell, so I'll do that next.) I've also set the battery power saving settings to never sleep (display or computer) in an effort to isolate the problem.

I've watched the temps and fan activity up to the point that it changes state and have not observed anything abnormal.

The SMC and PRAM resets were my first effort before posting.

Will try Safe Mode next.

In safe mode (with the 65W charger, which is a replacement for the original that was damaged) Everything was normal. Removed from A/C and exercised the system for 18 minutes (including connecting and disconnecting power after the 15 minute mark) and all was well. Previously it would only run 1.5 minutes after disconnecting power.

I'm now connected with an 80W charger that I tracked down. Time to see what happens when I disconnect it.

Going on 30 minutes after unplugging the adapter without a hitch.

Time to check all the chargers in the house and go pick up a replacement so I've got an 85W.

Which models use a 60W instead of an 85W?

I think it may have been this simple - which is quite shocking.

Then my daughter now has a spare.

So far, so good. Thanks for all the help. I would have never noticed the wattage issue.

Final resolution - the DC in board was zapped. New board, new battery, new charger and all is well. It does seem that Mavericks is more power-hungry than older versions of OS-X, but that can be mitigated a bit when battery life is critical.