Download here files that are mentioned in the blogs:
Quartus II project of Commodore 64 PLA chip - link to blog
Tapir - FN_save.tzx file - link to blog
PCB designs to calibrate etch testa in PDF format - link to blog
Schematics and PCB files for 555-timer chip in astable mode - link to blog
Inverted PCB layout in PDF format for 555-timer chip in astable mode - link to blog