AC Adapters: Do watts have to match? / Is 19v close enough to 20?
Is it okay to replace a 65w AC adapter for a laptop computer with 90 or 120w?


1)  Yes. As long as the wattage is higher, it's fine.


  Specifically, is it okay to replace a 20v adapter with a 19v one, for a laptop computer?


2) It depends on the device, but it will probably work. Devices generally will not be damaged by a voltage that's too low. They just may not  work correctly.