The C64 Diagnostic Rev. 586220 Harness also requires an (EPROM) cartridge, that is holding the software. Personally, I like bwack's Versa64Cart for that purpose, SukkoPera's OpenC64Cart works as well.
The C64 Dead Test Rev. 781220 is another test software, which was originally issued by Commodore for testing the C64. It is a very basic test and an important part is the RAM test. A broken RAM will be indicated by the number of fashes of the black screen. Without RAM, there is no proper display possible.
Since both test software are essential in the C64 repair workshop, it would be good to combine both on a single cartridge. Switching both might be a good thing.
It is not a big deal to burn both *.bin files on an EPROM, but there are some more settings required.
The A13 bit of the EPROM offset address is a result of placing the Diagnostic software from $0000 to $1FFF and the Dead Test from $2000 to $3FFF. (those are hexadecimal numbers). A14 and A15 are both LOW (for a 27C512 EPROM).
The goal is to set up the cartridge with a simple DPDT (Double Pole Double Throw) switch:
● One pole of this switch can clearly be /OE switching between /ROML and /ROMH.
● GND can be switched to either /GAME and /EXROM, since only one is low at a time and there are pull-up resistors in the C64, holding them HIGH.
● A13 is identical to /EXROM
This implies the solution for the switching problem:
Wiring diagram of the DPDT switch, which is connected to the Versa64Cart.
The Versa64Cart provides solder bridges for configuration, which results in a minimal requirement of parts. The schematic above shows this configuration for the 27C512 type EPROM:
● JP8 is bridged (= A15 is LOW)
● JP10 is bridged (=A14 is LOW)
● J5 is set to "Switch" (=/OE is in 8k mode)
For 27C256 type EPROMs, A15 has to be HIGH => JP8 is open and R2 is 10kOhm.
For 27C128 type EPROMs, both A15 and A14 have to be HIGH => JP8 and JP10 are open and R2 and R3 are both 10kOhm.
J5 is configured the same. A 27C64 does not make sense here, since it can only hold one software anyways.
The two binaries require merging:
Diagnostic Rev. 586220 @ $0000
Dead Test Rev. 781220 @ $2000
The binaries for that can be downloaded from World of Jani. A guide on how to merge multiple binary files to on image can be found on this website.
I have prepared an image with the Diagnostic Rev. 586220++ (v0.5) and the Dread Test Rev. 781220. Download it.
The cartridge case for the C64, which I have purchased from www.restore-store.de is pretty nice and slim. It provides the space for holding the switch. It does not allow a socket for the EPROM. Also, the Versa64Cart is a little bit to narrow, so I have created a 3D-print adapter, which holds the PCB centered.
Switch wired to the Versa64Cart
An alternative for the 3D printed adaptor (download the STL file) is just a little hot glue.
Cartridge case with 3D-printed adaptor