When i got to be MacBook Pro user, i had already before it lost trust towards Apple chargers after my friend asked to try fix his exploded charger. So at those times i went to recycle center get 230W HP charger which i modified to be MagSafe charger for me with chinese charger lead (they scammed me advertise to be 85W but wasn't and Pro models requires 85W charger to charge while being on!). First problem was drop the voltage under specs of MacBook Pro as i like play safe still though.

I have had this long time to write down this operation to share it for everyone who struggles to order overpriced bombs (Why Delta?!). Now was time as i was moving away from MacBook. So i took another HP charger as victim for operation (and make it more nicer looking).

MacBook Pro has spec of 16.5V - 18.5V but when i checked this charger voltage it hovered over 19V which i didn't like.

I found on forums some attempts to modify voltage on this but they went after chip which handles curent limit (HP3D6) on this charger. But as generic hint look for OP AMP (230W has dual OP AMP) and its circuitry. You find correct resistor divider circuitry by following chip's VREF and charger's VOUT line as with those you narrow down correct ones easily. Op Amp does read fraction of the VOUT over voltage divider resistors and which we does modify in the end. This one has generic 385 chip. I didn't so much read but i did go just now after locating resistors for this to change the higher one and check how it behaved. Results are on picture. For final i did aim 18,5V or slightly lower. There was too fine tune trim pot under glue/silicone next to Charger's LED indicator.

As an update HP 135W from LiteOn had TSM103AIW OP AMP which worked similarly.

MagSafe ID faking

In the end connector which you plug to MacBook is locating DS2413 1-wire chip, which does operate the LED lights (color) and communication towards MacBook Pro (Serial, Family.. etc). This chip has been used multiple manufacturers Dell, HP etc.. For MacBook Pro's you need use information which is for 85W charger so you get charging working while your MacBook Pro is turned on.

On Github found OneWireHub library, with example DS2502 emulation of Dell charger which i ended up using in this project.

Download: *.hex (Flash ready program - 8mhz) MD5: 9CF796146CC2E3020E358FD122B40692.

Here above is shortened circuitry and DC-DC converter (3.3V!) which shows then all pieces to put all together. Notice i used ready MagSafe connector which i disassembled and removed ID chip (as it was wrong) and replaced cable. Leds can be used if you connect that ID chip legs of Led to Ground. I put there 30mA fuse in series to make sure if Leds burn or go wrong it won't bring whole charger down.

Finishing

All together and ready to use. Hot glue is all sealed yes and good tip is that use something to heat it to make it more better attaching (it won't like cold surfaces to grab)

Writer won't help repair broken MacBook's. All is on YOU!