Magsafe barrel jack mod

[mustagcoupe]

My friend gave me an early 2011 MacBook pro 13 inch. The power adapter he included was a terrifying piece of aftermarket junk that wouldn't even charge the battery all the way. The only other magsafe adapter I had is also aftermarket and makes strange noises under load. I cut the cord off of one of the aftermarket chargers and measured the voltage coming out of it at a constant 19v DC. There are only 2 wires in the cord and it appears that all of the circuitry necessary to negotiate magsafe is in the magsafe plug itself. So I decided to see if you could just solder a barrel jack onto the other end of the magsafe cord and use it with a regular 18.5v PC charging brick. It works on both my 2009 polycarbonate MacBook and the 2011 MacBook pro. If you have a broken apple charger or a shady aftermarket one this could be a very cheap or free way to get a working charger. You just need a broken magsafe charger, a barrel jack, and a high quality PC laptop charger with a barrel plug.

 

[Needleroozer]

Nice job!

it appears that all of the circuitry necessary to negotiate magsafe is in the magsafe plug itself

Yep, there’s a simple ID chip in the plug that advertises how much power that cable can deliver; the MacBook will talk to that plug and then perform some power handshaking to activate an official Apple MagSafe charger, as detailed on Ken Shirrif’s wonderful site:

Teardown and exploration of Apple's Magsafe connector

Have you ever wondered what's inside a Mac's Magsafe connector? What controls the light? How does the Mac know what kind of charger it is? T...

www.righto.com

Bypassing that handshake, like you have done, makes the cable a little bit more dangerous in that you could get a minor shock if you lick the exposed end, but beyond that, it’ll work just the same.
All the power regulation happens in the MacBook, and I think that it should work with input voltages as low as 12V.

 

[mustagcoupe]

Bypassing that handshake, like you have done, makes the cable a little bit more dangerous in that you could get a minor shock if you lick the exposed end, but beyond that, it’ll work just the same.
All the power regulation happens in the MacBook, and I think that it should work with input voltages as low as 12V.

So you are saying the original apple magsafe brick will only output significant power once the chip in the end communicates with it? Both of the cheap dangerous aftermarket magsafe chargers I have just output a constant 19v even with the end with the chip cut off, I thought that was normal. Since both my aftermarket chargers output a constant 19v no matter what I wouldn't think my cable is any more dangerous than that. If anything I would think it's slightly safer because I'm using a high quality power brick with actual certifications and safety features. I took apart both fake chargers and they're honestly scary, no safety features at all, fake ground pins and they both have damaged components, poor build quality and extremely cheap and shady electrolytic capacitors.

 

[Needleroozer]

So you are saying the original apple magsafe brick will only output significant power once the chip in the end communicates with it? Both of the cheap dangerous aftermarket magsafe chargers I have just output a constant 19v even with the end with the chip cut off, I thought that was normal. Since both my aftermarket chargers output a constant 19v no matter what I wouldn't think my cable is any more dangerous than that. If anything I would think it's slightly safer because I'm using a high quality power brick with actual certifications and safety features. I took apart both fake chargers and they're honestly scary, no safety features at all, fake ground pins and they both have damaged components, poor build quality and extremely cheap and shady electrolytic capacitors.

Correct, the original Apple charger does that handshake with the laptop to enable the full-power output, but aftermarket ones do not bother.

I agree that your new charger brick is probably much higher quality than the knockoff MagSafe chargers, especially given what you’ve said.

 

[mustagcoupe]

Correct, the original Apple charger does that handshake with the laptop to enable the full-power output, but aftermarket ones do not bother.

I agree that your new charger brick is probably much higher quality than the knockoff MagSafe chargers, especially given what you’ve said.

Interesting. I didn't know they bothered doing that. I guess it makes sense with the pins exposed like that on the magsafe plug.

One benefit to my barrel jack adapter is you can use a larger power brick that will run much cooler than the apple one. I'm using a 120w brick with a 60w magsafe end so the computer will never ask for more than about 60w. The brick doesn't even get warm.

I did order a real apple power adapter just so I have one. I also ordered 16gb of memory for the 2011 MacBook pro and a new battery from owc. The battery it came with is some $20 aftermarket garbage from a company called SNSYIY. It's acting strangely and reporting odd things in coconut battery and I don't trust it.