This is an extension of my previous Joust thread, but I have a clearer mission now.
My Joust has recently become very consistent in crashing on wave 4 when there are plenty of enemies onscreen.
When you turn it on, it always gives a RAM 21 error. RAM 21 is verified good with a new socket. After the RAM test, the game boots as normal and the LED shows 0.
In wave 3, it will usually leave a copy of a buzzard (sans rider) on one side of the screen until something else moves into that space and paints over it.
When I get to wave 4, it usually keeps playing for a minute or two, but extra parts of enemies keep getting left on the screen. After that the screen flashes with several lines of garbage in the top third of the screen and the game's colors become inaccurate, and then the game resets back to the rug pattern.
So far, I have replaced the pin headers and connectors on the MPU and ROM boards along with all the sockets for the ROMs, decoder PROMs, and special chips, replaced the ROM ribbon cable, and have tried swapping out known good decoders, special chips, and PIAs. I have also tried my Robotron ROM board with my Joust MPU board and it boots up directly to 0. I am fairly confident there's a logic chip on the ROM board that is giving me problems but I don't know what to look for.
Either that, or maybe my power is bad, but my power supply board has been rebuilt and has good voltages.
The only other thing I can think of that I haven't done is validate the ROMs, but it doesn't seem like they would cause this problem.
If anyone has seen this happen before, please let me know what you think.
My Joust has recently become very consistent in crashing on wave 4 when there are plenty of enemies onscreen.
When you turn it on, it always gives a RAM 21 error. RAM 21 is verified good with a new socket. After the RAM test, the game boots as normal and the LED shows 0.
In wave 3, it will usually leave a copy of a buzzard (sans rider) on one side of the screen until something else moves into that space and paints over it.
When I get to wave 4, it usually keeps playing for a minute or two, but extra parts of enemies keep getting left on the screen. After that the screen flashes with several lines of garbage in the top third of the screen and the game's colors become inaccurate, and then the game resets back to the rug pattern.
So far, I have replaced the pin headers and connectors on the MPU and ROM boards along with all the sockets for the ROMs, decoder PROMs, and special chips, replaced the ROM ribbon cable, and have tried swapping out known good decoders, special chips, and PIAs. I have also tried my Robotron ROM board with my Joust MPU board and it boots up directly to 0. I am fairly confident there's a logic chip on the ROM board that is giving me problems but I don't know what to look for.
Either that, or maybe my power is bad, but my power supply board has been rebuilt and has good voltages.
The only other thing I can think of that I haven't done is validate the ROMs, but it doesn't seem like they would cause this problem.
If anyone has seen this happen before, please let me know what you think.
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