This is the first Jamma PCB I've looked at.
Basically lines across the screen, otherwise the title screen runs and a 2 player game coins up and plays fine.
Audio is good, all sounds checked okay in test menu..
Here's a link to the manual with a schematic.
There are two versions available but only this one has the schematics.
https://www.arcade-museum.com/manuals-videogames/C/Cal.50%20Universal%20Jamma%20Conversion%20Kit%20Instruction%20Manual%20With%20Schematics.pdfThis
It's much easier dealing with a single layer but the surface mount chips are a bitch.
I threw it on the test bench this afternoon and started to check all the TTL chips that I could with the logic probe.
I couldn't find anything out of the ordinary so I started to look at the other IC's.
To be honest I don't know what most of them are or what they do but the schematic made it easy enough to poke around and see what was happening.
I put the board into test mode and started to poke around.
I found no input at pins 34 and 43 on the chip at 7K (X1-002A U35).
I followed the lines back to the Mask ROMs and checked pin 15 at 6M and pin 17 at 5M and there was data.
I sent a pulse into the inputs at 7K and the pulse filled the lines on screen where the fault was happening.
I ran two temporary trace wires from the pins with no inputs to the Mask ROMs.
The image has improved but there are still some issues.
The faulty image you normally see on screen.
The good image inbetween cycles.
Pic of the original fault with the background.
The lines in the background have improved and are gone from the dog tags.
I'll keep looking at the lines between the Mask ROMs and the two chips at 7K and 8H and possibly replace the sockets just to be sure.
Kaizen0882017-04-12 00:50:00
Basically lines across the screen, otherwise the title screen runs and a 2 player game coins up and plays fine.
Audio is good, all sounds checked okay in test menu..
Here's a link to the manual with a schematic.
There are two versions available but only this one has the schematics.
https://www.arcade-museum.com/manuals-videogames/C/Cal.50%20Universal%20Jamma%20Conversion%20Kit%20Instruction%20Manual%20With%20Schematics.pdfThis
It's much easier dealing with a single layer but the surface mount chips are a bitch.
I threw it on the test bench this afternoon and started to check all the TTL chips that I could with the logic probe.
I couldn't find anything out of the ordinary so I started to look at the other IC's.
To be honest I don't know what most of them are or what they do but the schematic made it easy enough to poke around and see what was happening.
I put the board into test mode and started to poke around.
I found no input at pins 34 and 43 on the chip at 7K (X1-002A U35).
I followed the lines back to the Mask ROMs and checked pin 15 at 6M and pin 17 at 5M and there was data.
I sent a pulse into the inputs at 7K and the pulse filled the lines on screen where the fault was happening.
I ran two temporary trace wires from the pins with no inputs to the Mask ROMs.
The image has improved but there are still some issues.
The faulty image you normally see on screen.
The good image inbetween cycles.
Pic of the original fault with the background.
The lines in the background have improved and are gone from the dog tags.
I'll keep looking at the lines between the Mask ROMs and the two chips at 7K and 8H and possibly replace the sockets just to be sure.
Kaizen0882017-04-12 00:50:00
