Q-Bert pyramid gone

frytex

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Working on qbert when I turn it on the pyramid is gone. Everything seems to be there. I was told there is already a thread on this I just can't find it. So any help will be great.
 
This post has the troubleshooting doc attached, which gives some info on the background character generation and possible sources of failure:
http://forums.arcade-museum.com/showpost.php?p=1087020&postcount=10

There's a fair amount of logic around all this (since the purpose is to free up the CPU from manually drawing it all), so I would use that doc to narrow down which part is failing - background registers, RAM, ROM, DMA cycles, etc.

LeChuck
 
Check the jumpers on the board and make sure none are missing, in the wrong location or corroded.
 
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Are those unmarked blue parts (small ones) unmarked caps or jumpers? He called me today to ask me what they were, but I was driving and couldn't look it up. he was cleaning some corrosion and said he thought some were broken...
 
They are jumper caps and there are some that will cause the exact issue he is having. Its the first thing I check on a qbert board since they are easily knocked off in storage and can also corrode if you have acid damage on the board. They are standard .100 jumper caps like used on pc motherboards and hard drives. If you dont have any you can just bridge the solder pads on the backside of the pcb for the ones that require jumpers.
 
They are jumper caps and there are some that will cause the exact issue he is having. Its the first thing I check on a qbert board since they are easily knocked off in storage and can also corrode if you have acid damage on the board. They are standard .100 jumper caps like used on pc motherboards and hard drives.

.100? The manual listed unmarked non-polarized caps as .01uf and unmarked polarized as 10uf. Since these have no part designator in the manual, wouldn't they be the .01uf? BTW - we are talking about the ones that are just to the right of the ROMs, and sprinkled throughout the board...

Oh, and he had a bunch of corrosion on the board in that bottom left corner where the battery is located...
 
Im sorry, I thought you were talking about the blue jumper caps. Yes, the blue CAPACITORS are .01uf. The caps I was referring to are the jumpers that slide over the header posts. There are three banks of them in the picture I posted.
 
Im sorry, I thought you were talking about the blue jumper caps. Yes, the blue CAPACITORS are .01uf. The caps I was referring to are the jumpers that slide over the header posts. There are three banks of them in the picture I posted.
Do you happen to have the schematic refs for those jumpers? Just curious what they control - do you any of them affect background character generation? The dipswitches don't appear to control anything relevant.

I would expect that the self-test could figure out if the CPU mechanism for setting background characters is busted (assuming it can read back the values it's writing). So I'm guessing the issue is either with the logic that fetches the backgrounds, or with access to the ROM containing them.

LeChuck
 
I dont know what each jumper does and I dont think the manual makes any mention of them. I know there is at least one other game that runs on the same pcb so im guessing that they are changed depending on what game its running.
 
Im sorry, I thought you were talking about the blue jumper caps. Yes, the blue CAPACITORS are .01uf. The caps I was referring to are the jumpers that slide over the header posts. There are three banks of them in the picture I posted.

For clarification, he is asking about the items highlighted below...

qbertblue.png
 
Im sorry, I thought you were talking about the blue jumper caps. Yes, the blue CAPACITORS are .01uf. The caps I was referring to are the jumpers that slide over the header posts. There are three banks of them in the picture I posted.

For clarification, he is asking about the items highlighted below. They have a number on them as 1AZ073 - or something like that. What would he use as a replacement?

qbertblue.png
 
Yes, those are .01uf 50v axial caps. These are not causing the problem he is having. Like I said, check those jumpers first.
 
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Yes, those are .01uf 50v axial caps. These are not causing the problem he is having. Like I said, check those jumpers first.

Unfortunately, he no longer lives semi-local. he is now up by Little Rock. So, it'll have to wait until he comes back to check his thread...
 
You know I love working on games but I am tired of trying and thinking I may have fixed something only to find out I didn't. It can get very depressing after a while. I love the help from everyone and I love trying new things it just sucks when that is not the answer.
 
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