Alan173
Well-known member
After repairing all the boards on my Defender game I figured I would tackle my backup boardset (I like the abuse!
). All the boards are repaired except for my CPU and I have run into a dead end. Interesting enough there was another post from 2009 with the EXACT SAME issue I am having:
http://forums.arcade-museum.com/showthread.php?t=83845&highlight=defender+rug&page=6
Unfortunately the post had no resolution to the problem but here is a quick summary of what I have:
Game boots to a rug pattern that continues to cycle. LED's do not flash but just come on with lights 2 and 4 lit. All circuits on this CPU board check fine except the Page 0 Decoder Circuit. My 5P pin 6 is stuck high with the input from the ROM board pulsing but the input from 4K is stuck high. All of the inputs at 4K (pins 1, 2 & 3) are pulsing just like my working board but output pins 6 and 7 continue to be stuck high. Both 5P and 4K have been replaced - no change. I grounded pin 1 (A1) and it jumpstarts pins 6 and 7 to pulsing erratically...but that is as far as I can get. At 4K I have good inputs and bad outputs and have triple checked the chip is good. Totally confused???
Funny somebody had an identical problem as mine.
Any ideas from the Defender repair experts out there?
I have a strange short condition (5V to ground) I have been toying with....but don't know if I am going down the right path with that one.
Alan
http://forums.arcade-museum.com/showthread.php?t=83845&highlight=defender+rug&page=6
Unfortunately the post had no resolution to the problem but here is a quick summary of what I have:
Game boots to a rug pattern that continues to cycle. LED's do not flash but just come on with lights 2 and 4 lit. All circuits on this CPU board check fine except the Page 0 Decoder Circuit. My 5P pin 6 is stuck high with the input from the ROM board pulsing but the input from 4K is stuck high. All of the inputs at 4K (pins 1, 2 & 3) are pulsing just like my working board but output pins 6 and 7 continue to be stuck high. Both 5P and 4K have been replaced - no change. I grounded pin 1 (A1) and it jumpstarts pins 6 and 7 to pulsing erratically...but that is as far as I can get. At 4K I have good inputs and bad outputs and have triple checked the chip is good. Totally confused???
Funny somebody had an identical problem as mine.
Any ideas from the Defender repair experts out there?
I have a strange short condition (5V to ground) I have been toying with....but don't know if I am going down the right path with that one.
Alan
