Toasted Macbook, Arduino untouched? How is this possible?

Fried a late 2013 ed Macbook Pro yesterday. I just finally got my Temp and Co2 sensors set up and calibrated and reading out to the serial monitor. I had 7.6v plugged into Vin as well as being plugged into the laptop via USB. I went to hook my analog input into the 3.3v to verify I was actually getting 3.3v but inwittingly plugged the 7.6v wire into the 3.3v out. My macbook instantly powered down...... It turned back on and all I could see is the spinning pinwheel over a screen of white triangles.... it rebooted several times before shutting down with all fans spinning like crazy. I could do nothing else with it until finally it died completely.

Completely pissed off, I threw all my stuff in a box and never looked at it again until this morning. This morning I hooked up my arduino to my desktop and tested several pins... Everything is normal. I ran a test program to blink some leds and all worked great...

How is it possible to turn a $1500 machine into a paperweight while leaving the arduino in perfect operation?

When Vin/2 is >3.3V, exernal power is selected. With 3.3V suddenly at 7.6, USB power is connected. Guessing the 7.6V backfed thru 3.3V regulator to overdrive the 5V line and somehow the Mac was not happy with USB having 7.6V coming in on the power pin.

Luckily I am still under warranty

fluxinghappy: Luckily I am still under warranty

I am sure the warranty will not cover that.

Do you think it will pass as a power surge? It's only 6 mth old and is in mint condition besides the main board being fried that is

Don't know. However, the first rule of hardware is never work on any circuit that is powered up.

Yeah the problem with that was I was calibrating a co2 sensor that needs the heater running for 2 hours before measurement. If I disconnect it the readings are useless. First thing I checked was if the heater was on a separate circuit. It has a common ground with the rest of the circuit so I couldn't power it separately.

That probably doesn't make too much sense I'm not sure. But I tried everything. I just got cocky jumping the wires I guess. Won't happen again for sure. Feel so dumb. I was well aware of what could happen too. Plain ignorance.