Abrupt power off in windows / latest Linux.

From day one this Lenovo ideapad z70-80 has had issues with suddenly powering down in windows (7 or 10). I bought the laptop with the intent of mostly using Linux, so when Linux proved to be 100% stable I decided to keep the laptop and not send it in for warranty repair work. Even if I get it fixed, windows will never go on this laptop as being forced to use only Linux this long has shown me nothing I want to do actually needs windows.

What happens is in windows is after being on for a few minutes, the CPU fan kick in high, and then after a few more minutes the PC suddenly powers off. I can turn the PC back on right away like normal and start the cycle all over again.

In Linux, initially, it was rock solid. I was running Linux Mint 17.3 and had no issue. I updated to 18, the 18.2 again with no issues. Then about a month ago I decided to update all the packages to the latest version. The next reboot after that update brought the issue partly into Linux. If I cold boot the machine it is rock solid but if I put it to sleep then wake it, or change the power source, the CPU fan kicks in after a minute or two and eventually shuts down just as in windows.

I suspect something is faulty with power management as everything otherwise is normal with the computer. Temps I can measure are all within spec and the heat pipes are all clear and free of dust buildup.

If I could locate the power management ic I could try replacing that, assuming it is a surface mount chip and not a bga chip.

Thanks in advance.