Let's face it, repairing the good old Commodore 64 is becoming a dying art. Parts are becoming very scarce, brick and mortar service depots are all but virtually non-existant and picking up a new C64 isn't an option.
Retro computer collectors have had to take up the mantle of diagnosing and repairing their own machines. Thankfully there are a multitude of diagnostic cartridges out there to help you pinpoint what might be wrong with your system.
The guys over at Corei64 have developed a ZIF (Zero Insertion Force) socket version of the Premium Dual Diagnostic cartridge.
If you want to utilize the wide variety of C64 diagnostic eproms available without having to purchase multiple cartridges, one for each image, then look no further. The Corei64 cartridge comes with a ZIF socket so you can easily switch eproms and comes with a UV erasable eprom preflashed with the 781220 diagnostic rom image, as well as the 586220 dead test rom image.
You get a three position toggle switch that allows you to choose between the diagnostic and dead test roms and to bypass the cartridge completely. You also get a reset push button to issue a hard reset.
Combine this beauty with a full test harness and you have yourself everything you need to diagnose what is ailing your Commodore.
What you don't get is a case to protect your investment. I have created a 3D printable case for the ZIF Diagnostic Cartridge. The case allow for easy access and operation of the ZIF socket in addition to the rom selector switch and the reset button.