There are many diagnostic cartridges for the C64 which can help troubleshoot problems with broken or dead C64s. This new cartridge comes with three special features: it measures the 5V rail, which can cause problems with the machine, it shows the CPU clock, which can be the cause for black screens, if absent, and it can run three different diagnostic ROMs. The C64 Deadtest, C64 Diag and C128 Diag are selectable via a small switch. Let’s assemble this new troubleshooting tool and test it out!