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C64 Diagnostic and Dead Test Cartridge
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.


Signal
Diagnostic
Dead Test
/GAME
H
L
/EXROM
L
H
/OE (chip select)
/ROML
/ROMH
A13
L
H


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


The Super Diagnostic Cartridge
Since a 27C512 can hold more than just two software, it was pretty obvious, that the content of the should be extended. An additional switch could set A14, which would double the number of software inside the cartridge.

Another very useful thing is the
1541 diagnostic software from World of Jani. Especially the reverse knocking has fixed already three of my disk drives, that did not work anymore. I would call it a "must have". Jani told me, that whenever somebody mentions this software, he is getting attacked for not being the author of this software. No, he is not the author of every single bit of this software, but he has made a cartridge out of it, which is quite a bit of work and an effort, that requires our respect. Respect Jani, thank you for your work!

Most recently, Compadre Dan Tootill has found a new Diagnostic tool. It is the
C-64 Dead Test Rev STID 1.1.0. This is avaliable on Stefano Furiosi/STID's github.


STID dead test


Dan kindly provided the
bin-file, which is compiled from the sources from the STID's github.

Signal
Diagnostic
586220
Dead Test
781220
1541 Diagnostic
Dead Test STID 1.1.0
/GAME
H
L
H
L
/EXROM
L
H
L
H
/OE (chip select)
/ROML
/ROMH
/ROML
/ROMH
A13
L
H
L
H
A14
L
L
H
H
EPROM offset
address
$0000
$2000
$4000
$6000
SET #1
SET #2


The single binary files have been combined to one 32kb image, which you can
download here.


Wiring diagram of the "Super Diagnostic" cartridge





"Super Diagnostic" cartridge


The label was made prior to the discovery of the STID dead test. It might be a good idea to add a reset button to the Versa64Cart here. A TACT switch (6mm x 6mm) with a height of 9.5mm might be sufficient.