MacBook powers off about 1 second into boot
Hi, I'm trying to see if I can narrow the problem down any further; I suspect a logic board or heat sensor.
My laptop was running on battery, I left the room, and when I came back a while later it seemed to have gone to sleep. I pressed a key to wake it up and it made disk drive startup sounds but nothing else; the light on the front was still pulsing.
I figured the battery was low, so I plugged it in and the battery charged up fully according to the battery lights, but the computer still wouldn't wake up so I powered off. Now, if I try to turn it on, the fans and drives start spinning and then the whole thing just shuts down within about a second (it sounds as if you had held down the power button to shut off). There was a DVD in the drive but I couldn't even coax it into ejecting so ended up opening the drive case to remove the disc.
I'm pretty sure they replaced my main board when I brought it in for a display replacement a couple of years ago (the board qualified for replacement because of an NVIDIA GPU issue I think).
If I remove both DIMMs, I get a repeating single beep indicating no RAM — it seems content to run like this for ages. If I hold down the power button, it will stay on until the front light starts flashing rapidly, which I understand means it's looking for a firmware update, and then immediately turns off.
Other than that, I have tried:
- resetting the NVRAM (no change)
- resetting the SMC (no change other than faster spinning fans on the next boot attempt)
- swapping and removing DIMMs one at a time (no change)
- individually disconnecting each of the connectors (drives, sensors, fans, etc.) on the logic board and trying to boot; nothing of note except:
- * I didn't disconnect the keyboard connector, since I couldn't turn the power on in that case
- * with the the left I/O board connector off, the machine doesn't do anything
- trying A/C only, battery only, and both (same behaviour in all cases)
Does anybody have any other suggestions to narrow the problem down or a confident sense whether it's the logic board or not? I'm a bit thrown by it's ability to sit happily beeping with no RAM in.
Is this a good question?