If I press POWER all the lights are ON only for 2...

Question

I don't know the cause, but suddenly my laptop died and now when I press POWER all the lights are ON only for 2 secs and then OFF again.

I opened the case and identified a burned voltage regulator near the battery charging socket. I replaced it with an equivalent spare part, but the fault is not removed. I measured all the motherboard test poits, from the adaptor socket down to the battery and it seems it is working OK, especially that when the voltage regulator was burned it was not charging the battery.

Now with the battery in its place, the battery is charging, but the laptop is not starting.

Any helpful ideas?

Thank you in advance !