This install guide will show you how to make your Sony PlayStation region free by installing a Mayumi v4 PS1 modchip. These are mostly just neater versions of what have been available for a long time on the internet with no major changes. They offer the easiest install points for those with not much soldering experience.
Mayumi v4 Pinout
Sony PlayStation 10X PM-41 Mayumi v4 Solder Map
On the PSone revision of PlayStation there is no external reset button for the reset signal to change the mode of the Mayumi v4 modchip. For this reason it is wired to a voltage so the pin is not left floating.