The C64 Saver 2 is an open-source project intended to make overvoltage protection available and easy to make for anyone interested in using the old Commodore power brick together with the C64. The power brick is 20-30 years old and it is known for failure with overvoltage. This is caused sometimes because of broken solder joints on the regulator or the regulator itself failing.
I’ve pretty much always had an aftermarket brick for my C64, as the original died a few years after I got my original. I don’t think I should trust the almost three decade old replacement brick, so if I power up my C64 again, I’d like to build something like this to put in line between it and the brick.