My SSD was partitioned for Windows and macOS. I use the Macbook almost exclusively for Windows 10.
Mid 2012 MBP Retina 15" 2.3Ghz 8GB.
I recently began having problems booting into Windows. The machine would get to the blue Windows 10 logo before promptly turning off. This was also true for macOS, the apple logo and load bar would appear, progress to about 25% before turning off. No automatic restart with either.
I also use a Linux dist on a live USB. This OS also demonstrates the same behavior, I get to the loader, choose Live mode or Persistence, it halts for a moment then turns off.
For troubleshooting, I played around creating bootable media on a second laptop. A Windows and a macOS install media via USB both exhibit the exact same behavior. (During this process I also cleaned the macOS partition, so now only the Windows OS remains). Removing the SSD bears no effect on the outcome of any bootable USB media.
Mac Recovery behaves the same, loads fully over Wifi to 100% under the rotating globe, then turns off. Windows Safe mode exhibits the same behavior. Countless PRAM and SMC resets also performed.
To note: Whilst troubleshooting via bootable USB medias, I bricked the EFI chip with clover. (I still don't know how it ended up on a drive, as I only ever DL clean installations from source, and was the first time I'd heard of it). Since then I have a solderless EFi chip from Macunlocks which fixed the chime loop. The boot problem in question existed before this, and remains still, so not sure if it will play an effect, but worth mentioning.
I've removed the logic board, looking for possible damage or corrosion. The board looks almost new, nothing worth mentioning. Apple hardware test (extended) run twice, no problems found.
I'm running out of idea's. An interesting one for sure. All help appreciated.