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?
Solution 1:
Yes they're compatible, however if the wattage of the charger is less than what the MacBook needs, it may not charge while the MacBook is running. That's typically only a consideration when you're using a charger from a smaller MacBook on a larger one. It shouldn't cause a burning smell or other malfunction.
If you're smelling burning, I'd get it checked out. Those things have been known to melt, particularly around the Magsafe connector, or where the cable meets the power brick. Check for frayed wires, etc. But I doubt it's related to using it on a different MacBook.
Solution 2:
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.
Solution 3:
I had the exact same issue, old 85w brick as a back up for a new mbp. I kept the new brick at work in order to travel. I also had occasional smells until it ultimately failed and shorted. The plastic around the wiring at the brick melted away. No damage to the mbp.
I spoke with a fella at the Mac store who said the point where the wire meets the brick is a common failure point. Seems many users, myself included, would wrap the wiring too tight. Over time the wires fail. He suggested leaving and inch of leeway before wrapping tightly.