Chosen Solution
I have obviously broken one or more of the fuses in the one wire cirquit to the magsafe on my Macbook Pro 15” mid 2012. There is a guide for replaceing these on a 2009 model, but the T1 and T2 fuses are not located in the same spot on the 2012 model. Is there some guide or image displaying the location? And where can I get those fuses - MOSFETs?
Reference with the logic board model number and not the model of the MacBook, the number will be 820-3330 for your model and the label is located generally at the bottom right of the board (top-side). Check boardview and schematics for 820-3330 which you can find on the internet. On the MagSafe DC Power Jack circuit (also known as one-wire circuit) there is a component that commonly gets blown from the use of knock-off (aftermarket) chargers which is U6900. Replacing the chip will fix the problem if that is the case. U6900 is north-west of the keyboard connector as seen here:
There is only one Fuse on the power leg of the MagSafe connection on the logic board. There is no fuse(s) in the One-Wire sense line. The connection goes directly to U6900 for over voltage protection of the charging of the battery. Let’s start again what are your symptoms with your system? Review the MagSafe connector on your charger as well as the cord if either or worn or damages this could burn out some of the components on your logic board.
