Tapper board putting out too much Green??

HMOON

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I have a tapper board that is putting out green all the time. Has anyone seen problems like this on MCR boards. Looking to repair this, or at least attempt to myself. Any Ideas would be helpful...

Here is what I have done:

Initially I thought It was a monitor problem so I rebuilt the K7000 monitor that was in the machine. Same result.

I took the board out and put it in another tapper machine and the problem followed the board. I am pretty confident it is a board issue.

Would it be wise to replace all the ribbon cables?

I have a scope, logic probe, and a meter to work with if anyone has ideas????
 

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I know you said you rebuilt the monitor, but, stupid question, did you try tweaking the green drive and green bias on the monitor (assuming your monitor has these controls)?

Just making sure before you go any further.
 
I adjusted the drive and bias for RGB, and realized after rebuilding the monitor that it was working properly. When I mived the board the another machine the problem followed the board. The monitor is working as it should. The problem is the board...Just want to know where to begin with troubleshooting the board.
 
its been awhile, but, iirc, you can trace the green drive back to a set of transistors and resistors on the cpu pcb. Check the resistors - one may be out of spec or wrong. The next component downstream (again, going from memory) is an 82s09 ram. I've seen colors change a bit by just swapping that ram out, so i suspect it could be your culprit as well, but i'd check the transistors and resistors first.
 
cdjumlp, thanks for the reply. I was looking over the schematic see what you are referring to. I will start there and work my way backwards. It looks like a D to A at 11E (93419) that might have a stuck output as well?? Well see what happens.
 
the 82s09 and 93419 are interchangeable - that's the one i was speaking of.
 
You could always try to unload the cab as an "ultra rare prototype color Budweiser St. Patrick's Day Tapper" from the looks of that leprechaun customer. :)
 
Tapper is back.......Without excess green!!

I wanted to follow up on this as I just found some time to dedicate to fixing this problem. I checked the transistors in the green circuit as well as the resistors and they all look good (Q106-Q107 I believe). I then replaced the 82S09 chip at 11E and the excess green is gone and the game looks great!

Thanks to cdjump for providing me with the trouble shooting info...

-J
 
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