This is an old post, preserved for reference.
The products and services mentioned within are no longer available.
The first batch of VIC20 diagnostics cartridge kits sold out faster than I was expecting, and it's taken ages to get a new batch of PCBs after being messed around by the PCB house. I have now had the PCBs made elsewhere, so they are now back in stock.
user guide for the VIC20 Diagnostics cartridge to try to explain what all of these tests indicate
The kit will be available in two versions, the same loopback plugs with a choice of cartridges.
Dedicated diagnostics cartridge kitThis version comes with a dedicated diagnostics cartridge, with the VIC20 diagnostics ROM and the RAM it requires to run.
ROM/RAM Cartridge with diagnostics loopback kitThe other version comes with the DIP switch controlled ROM/RAM cartridge. Using the DIP switches, a series of ROM cartridges can be selected, includes the diagnostics ROM and a few games cartridges to test the system. It can also be used as a 27K or 32K RAM cartridge.
Penultimate Cartridge does not include the diagnostics ROM (you can't navigate the menu if your VIC20 is not working or if you have the keyboard loopback installed).
2022 Update: The Penultimate Cartridge includes a Dead Test that can run from the menu or by holding down reset. This is now available from The Future Was 8 bit