Today I read an artical about the laptop AC adapter can not work normal. I think it is really very useful and comprehensive. You can refer it if you have the same problem.
But, I have an suggestion to supplement according to my experience.
You should check whether the adapter model number(such as PA-1121-28 ), electric current(6.32A), adapter voltage(19V), adapter interface are the same. (the electric current, adapter voltage, adapter interface must be the same, if it is not. It can not be compatible.
This just my personal opinion. Just for your reference.