A little update. I took the CLK board off of the 4-board stack and ohm'd out the 4 logic chips that are socketed. They were all fine, and their diode junction signatures seemed to all match each other (except for when two had certain pins grounded vs. not on the other two, etc..). There is also a PROM at 5F on the CPU board (if I remember correctly) that was pretty corroded on the pins. I just cleaned it up and resocketed it. Trying the board again tonight yielded no new changes unfortunately.
One more thing I tried was flipping the dip switches on and off a bunch to see it they were open, and maybe fixing them. I still want to ohm them out and see if they are good, but that didn't help or change anything.
I decided to try to make a small step forward and fix the vertical tearing as shown in the first pics of this thread. I didn't want to mess with the pots on the monitor since they worked for the Donkey Kong 3 board set just fine, so I started playing with VR1 and VR2 on the Donkey Kong 4-board set. It turns out that VR2 (left/right adj.) fixed the tearing problem. I think the pot was just dirty so I tweaked it back and forth a bunch and now it adjusts the picture left and right and only does the tearing in a few spots.
So searching through posts on rec.games.video.arcade.collecting yielded something REALLY interesting. Someone with the exact same problem as me!
CHECK OUT THE THREAD HEREHe tried a bunch of different stuff, and even replaced the ROMs, and still no change. I've posted/emailed him to find out if he ever fixed it, but it's not hopeful. Still though, this is at least encouraging that some -one- thing is failing and causing this to happen.
It's interesting to note that I've found many people reporting that the JUMP sound is the first sound they hear when powering up the machine (
even though MAME makes a DK growl sound upon startup See below for the correction on this). As if the machine is starting to execute the right code, and then starts to screw up big time and goes into a loop of garbage characters and the death sound. Actually it's interesting to note also that the characters on the looping screen are the mario 1-up sprites over and over again, in slightly different shades. It seems like the addressing is seriously messed up, to the point where the same section of RAM or ROM is being accessed over and over again.
Does anybody have any expert advice on how to debug this with MAME in debugging mode? Can I simulate RAM failures and addressing failures easily? I think I might need to replace the RAM and/or check all traces that address and select the RAM.
-Brett
edit: corrected myself