A guide to replaceing a dead C64 PLA with 27C512 EPROM
1. Desolder the PLA once you have confirmed it to be faulty. 2. Obtain a 27C512 EPROM. Some have reported that only 45ns rated EPROMs work, however I used a salvaged 150ns EPROM and it works fine. Results may vary depending on the revision C64 and the type and speed of DRAM in your particular C64. 3. Burn the binary file into the EPROM. 4. Construct the adapter. See images below for a couple of ideas on how to go about doing that.
5. Power up, and if everything went well you should see the familiar startup screen.
6. Double check your adapter wiring if it doesn't work, failing that your EPROM may not be compatible. If you have any questions you can email me at firstname.lastname@example.org
The adapter circuit diagram. Credit to Ray Carlsen. (http://staff.washington.edu/rrcc/)
The PLA removed from a breadbox C64.
Breadbox C64, Willem EPROM programmer, EPROMs and modified Magic Desk cartridge used for development.
First version of the PLA-27C512 adapter, sandwiched DIL sockets.
Second version of the PLA-27C512 adapter, breadboard construction.
C64 mainboard with PLA-27C512 adapter installed.
Shown in operation.