My compaq nc 6220 laptop has a problem when i plug in the adapter the power indicator stands in for some few seconds then goes off. When the power indicator light is on and i press on the power button it does not come on unless the indicator light goes off.
It could be a bad AC adapter or perhaps a bad jack. You can test to see what the issue is if you have access to another AC adapter, i.e. if it works, then you know it's the AC adapter. However, I've noticed a lot of issues with the power jacks in Compaq computers though, so it could be that.