I'm using one of my old laptops as a server. I'm running the laptop without battery in case of a need for a hard reset. When I need a hard reset, I want to be able make this happen with a toggle of AC power. The problem is, when AC power lost and come back, the laptop can not be powered on automatically. Unlike desktop computers' BIOS, most laptop's BIOS including mine does not have such power settings and no "wake on lan" option.
So I decided to hack the power button. If I touch a 1 uF capacitor by parallel, laptop powers on. This is good. If I solder this capacitor in the same place, the laptop is not getting up when AC power come back.
Why would it happen?
The laptop expects power button released in the firs place, and then pressed for a short time. What I did causes "pressing button as soon as the AC power comes" effect. That was why battery led is flashing when I solder the capacitor to the pins of the power switch.
Answer is added: https://electronics.stackexchange.com/a/145588/20285