This is the case-less version of the Commodore 64  Diagnostic and Dead Test Cartridge, two cartridges in one.

This new version 4 includes a built in reset button as well.

This is a gold plated cartridge.  Unlike the boards with the "tin" style cartridge edges, this version won't damage your cartridge port by wearing and clogging your port.  Further, it is designed to fit in a standard cartridge shell that supports a center screw.

This unique cartridge includes both the 781220 diagnostic cartridge, as well as the 586220 dead test cartridge.  Both of these cartridges are available to you on this one cartridge.  Simply flip the switch to toggle between the two.  This cartridge also features a color changing RGB power light (indicating that your computer is supplying voltage on the 5V line).

Works on all Commodore 64 Models. 

This is the Cartridge you'll need if your Commodore starts with a Blank Screen or even if boots with some defective components. Identifies what chip/chips need to be replaced. 

Works on both NTSC and PAL computers.

This is the same Cartridge that was used by Commodore Technicians to repair faulty Commodores. Dead test can take 20+ seconds to boot up).  The current version of the board has a red PCB color.