Can't turn power on sometimes

[pppmmm]

My T60 has power problems. Sometimes (and lately it's been quite often) I want to power it on. The LED indicators are not working well either. When I plug the AC adapter, it shows no light. I've managed to turn it on lately leaving the adapter plugged in and waiting a couple of hours. After that, everything worked as normal.
It is very annoying, so I've been leaving the PC in suspend mode whenever I'm not using it.

Do you have any idea what could be causing this? What can I do?
It's a T60 model 2007-43Y

[Harryc]

Measure the center pin of the AC adapter for 20VDC with a multimeter.