Chosen Solution
MacBook Pro 13" Unibody Mid 2012, starts up and shuts immediate off, when connected to the Magsafe. Then it stays in a Bootloop/Black screen shutdown (and infinite repeat). More information can be seen via https://youtu.be/zues-vTE4C4. Things I’ve tried. SMC reset. (won’t even get the possibility to try)PRAM reset (won’t even get the possibility to try)Take battery out, connected with MagsafeVerbose/Single User Mode (won’t even get the possibility to try) Unfortunately there hasn’t been a solution. Does anyone know which problem this could be? Update (06/04/2019) Unfortunately I haven’t found corrosion on the Logicboard.
Any other possibilities that can work? Update (06/04/2019) When RAM not inserted, it will beep: One tone, repeating every five seconds: No RAM is installed. If you recently replaced or upgraded your computer’s RAM, check to see if it was installed properly. https://support.apple.com/en-us/HT202768 Unfortunately when RAM back inserted, it will get the same Bootloop/Black screen. Update (06/04/2019) Checked RAM-memory, and the two RAM-slots. Still no solution, to Boot the MacBook Pro. RAM 1 2 (both memory sticks)RAM 2 1 (changed memorysticks order)RAM 1 (One single RAM in slot 1*)RAM 2 (One single RAM in slot 2*) *both memorystick tested.
Generally this is caused by liquid damage near the top section (edge) of the logic board. Moisture likes to get in through the air vents which are located near the bottom of the screen. Try a barebones test in case someone like a hard drive is causing it to not stay on, so this would be like having the camera, optical drive, hard drive, battery indicator light, keyboard, keyboard backlight unplugged, no need to take the board out for this one and see if it stays on. If there are corroded components on the board (liquid damage) these generally need some resistors, capacitors and IC components that need to be replaced. As the MacBook is semi-working the damage shouldn’t be too bad and can be fixed by someone locally that does micro-soldering / board repairs for MacBooks.