Is an older MagSafe power adapter compatible with a newer model MacBook Pro? I'm using the MagSafe power adapter from my old multibody Macbook Pro:



On my new unibody Macbook Pro:



The MagSafe power adapter has become very hot and emitting a faint burning smell. It's not scalding hot. I can still hold it in my hand. If I were to guess, it's 150 Fahrenheit. The smell is similar to what you would smell when you turn on a cheap blender for too long. It is properly charging though. I see the percentage increase on my screen. I'm not in a foreign country, so voltage is not the issue. So I'm wondering, is the unibody Mac not compatible with the multibody Mac's power brick?
Yes - an 85 W magsafe adapter is an 85 W magsafe adapter no matter what the end cord arrangement. The newer adapters have a thin barrel more like the 45 W macbook air barrel style adapters first required due to the limited space where it connected.

The heat and burning smell could be a safety issue (especially if your sniffer isn't very sentitive)  - have it looked at by a professional that sees a lot of adapters or just replace it if your sense it it's not working properly.