I have acquired an AC adapter, which is 90W 20V. Can I use this with my R500? Where can I go to check if an adapter is compatible for use with my machine?
First, look at the FRU number on the adapter and then check it against this list.
The FRU can be located on the underside of the adapter, located in the picture attached.
An original Lenovo adapter with the correct large diameter (compared to smaller diameter tips used on T43, R51 and prior models) can then be used with your R500. A 90w adapter may also be used.