Acer 5920G not powering up

Nothing happens when I press the power button of my Acer 5920G.

The mains adapter light is solid green and the only external sign of life from the laptop is the blue light from the L-shaped slot to the left of the power button. There are no other LEDs illuminated and no action from the cooling fan, HDD or optical drive. I've read that this model can have a problem with the graphics card dying through overheating and this one has the 8600M GT which seems to have more than its fair share of this issue.

If that was the problem it would be a good opportunity to upgrade to a better card but I'd expect some initial action from other components even if there's no POST. I've tried another power board but that didn't help. Is there a chance that it's just a graphics card failure or does it sound more like a motherboard component issue and if so where should I check?

 

Here below are possible causes and troubleshooting steps of laptop that can't power on, hope it may help:
Possible causes:
1. AC adapter failure.
2. Power jack failure.
3. Motherboard failure.
Possible troubleshooting steps and repair solutions:

1. Test the AC adapter with a digital multimeter. It's possible that you have a failed AC adapter. If you don't have a multimeter, test your laptop with another known good AC adapter.

2.It's possible that power jack (socket where you plug the AC adapter) is broken. Remove the motherboard and take a closer look at the power jack. In some cases you can fix the jack by resoldering it on the motherboard. In other cases you have to replace the jack with a new one. Using a multimeter, test if the power goes to the motherboard through the jack.

3. If replacing the AC power adapter and jack on the motherboard doesn't help, most likely you have a bad motherboard. Replace the motherboard.

 

Thanks, I've checked for power at the PJ1 socket so it's a motherboard fault. When I can make some time I'll check for faulty capacitors etc. as a quick check shows 12.46v on the drains of a couple of triodes near the battery connector, although that's likely to be a secondary problem.

 

@ruruliu: It could also be a power button failure. It's surprisingly common.