help: Exidy Venture, weird color problem

joemagiera

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Working on an Exidy Venture PCB (version 5 set 1 or 2). No boot up error messages. Game plays fine. All sounds play fine. I'm having some color problems and I don't know where to start on this one. You don't even need to play the game, you can see the issue in attract mode. When you are in the main screen, and then go into one of rooms, the main screen goes away and the room you just entered expands on the screen and now you are viewing just the individual room (that has been expanded). My issue is if you look at MAME when you do this, the walls around you on the expanded room are purple. In my game the walls are yellow. I thought I was missing the color blue, but that is not the case. When you are looking at the text screens in attract mode in MAME, the words are generally white, with some words having a blue highlight. When the game is booting up, it says "stand by version 5". In MAME this is a light blue. On my game, it's white, and all the text is white, which is why I thought I was missing blue.

You can see a video of the issue here:
https://missilecommand.org/long_distance_repair/Exidy_Venture/Venture_blue_mystery.mp4

Also, very likely a main board issue as I have a second sound board doing the exact same thing.

Anyone have any ideas?

Joe
 
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Working on an Exidy Venture PCB (version 5 set 1 or 2). No boot up error messages. Game plays fine. All sounds play fine. I'm having some color problems and I don't know where to start on this one. You don't even need to play the game, you can see the issue in attract mode. When you are in the main screen, and then go into one of rooms, the main screen goes away and the room you just entered expands on the screen and now you are viewing just the individual room (that has been expanded). My issue is if you look at MAME when you do this, the walls around you on the expanded room are purple. In my game the walls are yellow. I thought I was missing the color blue, but that is not the case. When you are looking at the text screens in attract mode in MAME, the words are generally white, with some words having a blue highlight. When the game is booting up, it says "stand by version 5". In MAME this is a light blue. On my game, it's white, and all the text is white, which is why I thought I was missing blue.

You can see a video of the issue here:
https://missilecommand.org/long_distance_repair/Exidy_Venture/Venture_blue_mystery.mp4

Also, very likely a main board issue as I have a second sound board doing the exact same thing.

Anyone have any ideas?

Joe
It looks like you might have green and blue swapped. Maybe a test cable/connector issue?
 
When blue is absent, I would try to backtrack through this circuit to find a stuck or missing signal.
Could be the mux, or latch or encoder etc. Sometimes piggybacking can provide a clue too. YMMV
This assumes it's an issue on the smaller board. But OP seems to imply it happens with another board.

So, then also remember to reflow the interboard headers. I've had issues with those and errant colors.
And lastly, if not the smaller board, review the signals from the main board shown below as inputs to the flip-flops?

Venture_Blue.jpg
 
When blue is absent, I would try to backtrack through this circuit to find a stuck or missing signal.
Could be the mux, or latch or encoder etc. Sometimes piggybacking can provide a clue too. YMMV
This assumes it's an issue on the smaller board. But OP seems to imply it happens with another board.

So, then also remember to reflow the interboard headers. I've had issues with those and errant colors.
And lastly, if not the smaller board, review the signals from the main board shown below as inputs to the flip-flops?

Venture_Blue.jpg
You might want to watch the video the OP posted. It shows clearly that blue is NOT missing. In fact he disconnects the red and green and leaves ONLY the blue and there's a complete picture on some of the screens. Your whole post will mislead him. This is why I assumed green and blue were swapped. His complaint was the walls of the room were "Yellow" (this is RED + GREEN with NO BLUE) instead of "Purple" (this is RED + BLUE with NO GREEN) so swapping GREEN and BLUE should have fixed that specifically. It may not have fixed other color problems but when he made the swap he just said it's "worse" and didn't provide any other information on what "worse" was OR if the wall color changed to purple. (this would verify he actually did swap the correct colors). If swapping the colors DID change the walls to purple but also made other object colors MORE incorrect then it's likely an issue with the generation of the VD7A10 or VA9 signals on the game board (since he mentioned he tried two different color boards and they both did the same thing). It's also possible he is mixing 1BPP board sets with 2BPP board sets. This will also cause incorrect colors to be displayed.
 
It's also possible he is mixing 1BPP board sets with 2BPP board sets. This will also cause incorrect colors to be displayed.
I will post a video of green and blue swapped today.

What are you referring to with 1BPP and 2BPP?
 
what color was the wall with the swap? Did the yellow wall become purple?

"worse" isn't really a helpful description, maybe post updated vid?
toledoflyer, my apologies. You asked a legitimate question and I gave you a bad answer.

Here's a video with blue & green swapped. Unfortunately I recorded it in slow motion which makes the camera sync even worse and completely garbles the speech, but it gives you the idea (turn down/off the sound). Also, this video is with all colors on the monitor turned on.

https://missilecommand.org/long_distance_repair/Exidy_Venture/Venture_green-blue_swapped.mp4
 
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Fax and Pepper II sprites are 2BPP, and have a different pinout on the DIP ribbon cable.
Whoa! You might have hit this. The main board was originally a Fax boardset that I'm trying to convert to a Venture.

What about Spectar? Are the ribbon cable pins the same as Venture?

Well, I suspect the ribbon cable itself is the same, but the traces on the board leading up to the ribbon cable are different? Do you know off hand how involved the differences are?
 
Neither board should use 5LINES, you can just pull that up.
VA9 matters though.
...and the addressing changes to the 6C prom...
Sincere thank you Mark. I'm going out of town for a bit, so it will be a while until I can work on this again, but I will definitely report back.

If neither board uses 5LINES or DBDIR, couldn't I just leave those in place?
 
Correcting the ribbon cable for pins 11 & 12 fixed. All working now.

Thanks all, and extra thanks to Mark/HudsonArcade for the final fix.
 

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