Robotron Sprite Issue?

Constellation

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So I got my Robotron fully working, or so I thought! I thought this was normal until I watched some game play. But after certain in game characters, they have these dots that follow them everywhere they go. If you run over the dots, they go away, but elsewise, they stay on the screen.

Any ideas?

AuLEJdyl.jpg
 
Most likely a special chip issue. There's no Sprites used in the Williams hardware, instead they use special chips to move blocks of memory from rom to ram or ram to ram. These are the two 40 pin chips next to each other on the ROM board.
 
Thanks Toledo! I pulled all the ROM chips out and cleaned and reseated. No change. I didn't know about those two 40 pin chips even though I saw them, so I didn't pull them. I'll do that tomorrow!
 
So to further update this. I pulled those chips and cleaned them. The game was better.....then about 2 minutes later, it came back. I pulled them, hit them with an eraser and deoxit again, and it was better.....two minutes later, it came back......frustrating!
 
So I got my Robotron fully working, or so I thought! I thought this was normal until I watched some game play. But after certain in game characters, they have these dots that follow them everywhere they go. If you run over the dots, they go away, but elsewise, they stay on the screen.

Any ideas?

AuLEJdyl.jpg
What is the weirdest error I've ever seen. How can Robotron hardware display the marquees for Asteroids, Ms. Pac-man and Pole Position, as shown in your picture? Reversed even? Truly weird! [emoji28]

Good luck.

In all seriousness, it sounds like you've identified the location, but the issue could still be those ICs (special chips) unless you've swapped in new or otherwise known good ICs. One or both of the sockets or their solder joints could also be the cause. Do you have another ROM board to swap in?

Scott C.
 
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What is the weirdest error I've ever seen. How can Robotron hardware display the marquees for Asteroids, Ms. Pac-man and Pole Position, as shown in your picture? Reversed even? Truly weird! [emoji28]

Good luck.

In all seriousness, it sounds like you've identified the location, but the issue could still be those ICs (special chips) unless you've swapped in new or otherwise known good ICs. One or both of the sockets or their solder joints could also be the cause. Do you have another ROM board to swap in?

Scott C.


Sadly - I do not have another ROM board to swap in it's place. Are you aware of a place/person that sells just these chips? If not, i'll have to look for a Robotron ROM board. :(
 
Try changing locations of the special chips. Each of them is responsible for 4 bits of the 8 bit byte that moves. If swapping them doesn't cause the output to change, it could be something else. I would get into the diagnostics and let it run the RAM test overnight and verify there are no issues found.

A Joust ROM board will work as well. Does your Robotron ROM board have the small board with the 74LS245 and resistor pack on it? If so, check the socket and pins on that board as well.

Good Luck. These special chips are failing in larger numbers and finding one is really a crap shoot.

Kirk S.
 
Try changing locations of the special chips. Each of them is responsible for 4 bits of the 8 bit byte that moves. If swapping them doesn't cause the output to change, it could be something else. I would get into the diagnostics and let it run the RAM test overnight and verify there are no issues found.

A Joust ROM board will work as well. Does your Robotron ROM board have the small board with the 74LS245 and resistor pack on it? If so, check the socket and pins on that board as well.

Good Luck. These special chips are failing in larger numbers and finding one is really a crap shoot.

Kirk S.


I switched the two chips - I didn't even know you could do this and it FIXED the issue.....for about 10 minutes. The wife and I played 3 games, and then I let it go to Attract mode, and then it came back.....after the same creatures. (The hulks).
 
Are you sure this isn't ribbon cable related? I've seen similar graphics problems with ROM board ribbon cable issues. Try wiggling it while playing to see if things change.
 
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