Last year, I acquired my first VIC-20 and when I discovered that someone shared the Gerber files for a fairly recent version of the Final Expansion 3 (english) for that machine on Github, I decided to set out and build one of those, of course. The FE3 might be a story for a later post, though. Because in order to build that cartridge, I first had to find an affordable way to program the ATF1504 CPLD that is used here.
The original external power supply for the Commodore 64 comes in different forms but they all have one thing in common: With increasing age they are prone to failure and when they finally break they are likely to destroy the precious computer they were powering.
The power brick for the Commodore delivers both 9V AC and 5V DC, the latter being produced from 9V AC with a voltage rectifier and a linear voltage regulator. While this voltage regulator is generally very reliable, it has to operate at the upper limit of its specification which takes its toll after decades of use. When the regulator finally breaks, it tends to short internally, thus supplying the sensitive TTL ICs inside the C64 with up to 9V instead of 5V since there is no integrated over-voltage protection.