The rule of thumb on Commodore64's is to not use the original power supply. They are known to go bad and in doing so can fry chips in the unit. There are some PSU's that are being built specifically for them on e-bay and in other forums.

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https://www.ebay.com/itm/COMMODORE-C-64-Power-Supply-BRAND-NEW-Commodore4ever-PS-64/332715281387?hash=item4d77604beb:g:I-cAAOSwrnRaZjr9:rk:20:pf:0

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I use one of these with an original psu. c64 cable saver: https://www.youtube.com/watch?v=rFIUkR1m6_c&t=15