Why do laptops start on their own

[Scootie]

Hi,
Since a few months I dweld myself into some light laptop repairs, mainly reballing and now I also tried out some bios flashings. Btw, I work in at an IT sale store hence the need to try and repair these units. There is still a lot for me to learn, still need to catch the magic of reading laptop schematics.

My first question for today is: Why do some laptops start on their own the moment when ac adapter is conected to them. I noticed this at quite a few laptops and can't figure out quite why?

Any ideas where to look for troubles?

Simptoms for these troubles vary from laptop to laptop:
- laptop starts up on ac adapter conect but no vga,
- starts up on ac adapter with vga and performs well and can be shutdown
and a few other examples but I dont want to bring up that many examples.

[spleenharvester]

Re: Why do laptops start on their own

Some laptops, particularly Dells, have a start-on-AC option in the BIOS. That's worth checking.

[Scootie]

Re: Why do laptops start on their own

The laptops I've had so far were 3xAcer(5740g, 5735) and 1xHP Compaq 6735s(autostart but no vga) and they didnt have this option in the bios so I assume something is bad in there.

[lefos]

Re: Why do laptops start on their own

Sometimes low rtc battery voltage might be the problem.
Also check for any liquid damage on keyboard / media buttons board.

[spidey]

Re: Why do laptops start on their own

mostly rtc battery.

[sasser]

Re: Why do laptops start on their own

i got one netbook lenovo s100. connected charger and power on and laptops start on their own without press button. also no display. no current on processor and intel nm10

[spleenharvester]

Re: Why do laptops start on their own

Hmm, I'd be interested to know if anyone finds anything on this. Maybe KBC fault? Presumably any short on the 3v rail connected to the power button, or anything that stops that 3v voltage being generated, is able to cause an auto power on?