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    Thread: Taito Space Invaders. Rolling screen.

    1. #11
      aaablettt's Avatar
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      Ok,
      Rechecked 6B and I had missed the output pin 8. Rookie mistake. Replaced 74LS55. Working.

      Next I need to figure out how to fix the missing


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    2. #12
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      Thanks guys for those who were prepared to help including Kaizen and Ro on the blower.


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    3. #13
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      Thumbs up

      Great to see you got it fixed in the end. Well done mate!

    4. #14
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      Nice work. Hadn't thought about the output as I assumed the h-sync was being done by the same IC and would have had more picture issues if the h-sync wasn't working. Guess the h-sync is done another way.

      Might be worth a quick write up in the repair logs incase someone else ends up with the same issue.

      Quote Originally Posted by aaablettt View Post
      Next I need to figure out how to fix the missing
      With regards to the eyes, that is quite strange. If it was a data problem you'd expect only certain chars with no eyes. The other through I had was that potentially the signals were having trouble going low after being high for a while, but that would mean the antenna would have the same problem.
      Last edited by crackedMagnet; 13th August 2017 at 08:09 AM. Reason: didn't notice the missing eye remark.

    5. #15
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      Thanks for your replies Matt.
      Its awesome when you guys take the time to write your views down for consideration. Another perspective is always welcome.
      The eyes....
      I'll swap out a daughter board to eliminate that part of the equation and come back.


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    6. #16
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      The problem originates on the daughter board. Some probing necessary.


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    7. #17
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      Re the missing :
      Thought through the problem like this...
      The Braze kit does a self test and says bit fail.
      I look at the data bus on the daughter board and see 8 ICs that run the bus. They are unmarked on the schematics I have and added to that the three data select pins on theses 8 chips (74LS151) were not connected on the board as depicted on the schematics. So, I probed the data select pins 9,10 & 11. Two of these pins; 9 & 10 both wiggled at some stage during the attract or game play but pin 11 was held low.
      That prompted me to look at the controlling IC (74175) at locn. [5] and to find the pin that is tied to pin 11 on the 8 x (74151). It turned out to be pin 2 on [5].
      I cut the pin 2 [5] with an eye to resolder if I was wrong but the signs were good.
      I am waiting for a 74175 to replace [5].


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    8. #18
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      Found a 74175; fixed.


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