Two millipede boards both have same issues

Smitty420

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So I've got two millipede boards that are giving me the same error codes. I am gettin R4 error and EA error.

One board has reset glitches put it into test mode and left it on and still had reset glitches. Pulled both pokeys to see if any change. Still gettin flicker like it wants to reset but not quite there. Plays with no mushrooms for a couple of seconds and then resets.


The other board seems to still play ok and also works with multipede installed.
 
If memory serves me. I haven't touched these boards in about a year. One was working with no errors at on point and the other I purchased not working and got it to this point. Started checking sockets and found broken pins on both grafics ROM locations. Replacing those and I expect the resetting to stop. And then I plan to replace socket for EARom To see if that helps.
 
Graphics roms broken pins will not cause a reset unless they bridge some traces, the earoms usually one or more of the below

bad earom chip
bad voltage regulator
Bad 555 timers
 
Graphics roms broken pins will not cause a reset unless they bridge some traces, the earoms usually one or more of the below

bad earom chip
bad voltage regulator
Bad 555 timers

I guess I replace the sockets because they were bad and hope for the best?

Then I look into the 555 timers as I'm pretty sure I've checked for voltage in latter days.
But I'll be checking that again also. Not sure about the other rom error. Wonder what both boards do the same thing, kinda. Now I just need a few days off to play with the games.
 
Ok so I got into the boards today and found the one I will call the original game board as it matches serial numbers for the game and board 2 will I will just call board 2

So the original board appears to have a bad 7915 as I am getting -38V at test points. I assume that when I replace this voltage regulator this might fix the EA rom error. This board was working perfectly at one point.

Board 2 has more problems even tho it shows the same errors. After replacing the graphics sockets it has clean graphics but the Archer disappears and the arrow appear to be coming from off the bottom of the screen. I can still move them left and right but all from the bottom. I also can't be killed as the archer is not on the screen. Also the background graphics appear to be correct, but the motion objects will flicker and glitch in and out. Eventually the game will go int reset mode and start watchdogging I believe.. I just keep cycling it rather than test for watchdogging at this point. Next Step? I guess I will start with the watchdogging next time it cycles but I must have problems with my motion graphics that eventually just causes the board failure.

Voltage at EARom appears to be constant but then it seems to drop off until i re adjust my meter and then it does the same thing -28V and then seems to fall off.. strange
 
If your 7915 was bad there's a good chance that was the earom issue
Your archer issue is an issue in the sprite circuitry are your centipedes also at the bottom of the screen?
 
If your 7915 was bad there's a good chance that was the earom issue
Your archer issue is an issue in the sprite circuitry are your centipedes also at the bottom of the screen?

Yea the 7915 was the EARom issue on Board one main game board and now I'm just getting the R4 error Rom H1. I swapped it out with the one from the other board and no change. I guess its time to get out the Rom Test setup and see what's up. It's been a while since I've seen this equipment.

Not sure whats up with board 2. Millipede disappears occasionally and jumps around. One time it broke up and the segments were spread out all over the screen. Ive tested both 7483's and a few other chips in the motion circuit. Everything I test seems to be good. Very Strange. It's been on for a while now with no resets at this point. I forgot to Reset the EARom on this board after replacing socket, Im thinking that this might be working but I still need a 7915 for this board as well


Will Try to get board one up and running with no errors and work on board 2 after I get some more voltage regulators.
 
Now board one is working solid no errors and no faults when playing. Seems the voltage regulator was the culprit and I rewrote the bad rom which now verifies. Game plays no problems.

Board two on the other hand had a bad EARom and same rewrote bad h1 rom and now no errors except the EARom which is missing as the chip was bad. Waiting in new chip.
The board plays until heated up a bit and then threw a bad ram error 1 beeps. Replaced ram and now no error put bad chip in socket confirmed bad. So replacing the chip game is palpable until start getting errors with motion objects. The archer disappears past the bottom and the worm is moved up and down by trackball limited by the archers amount of movement. Motion graphics jump around occasionally. Archer reappears and still no errors in test mode. Maybe a bad counter?
 
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