rmcelwee
Member
Dangerous noob with a logic probe looking at a D780 cpu...
Short description - Wait pin shows a steady high rhythmic pulse.
Long description:
I have two Zaxxon boardsets. One with a working "A" board and one with a non-working "A" board. The bad board will display the high score table during attract mode but when it tries to show the game action during the attract it just displays a blank screen. I see that WAIT on the working board is HIGH during the high score display and is rapidly pulsing during the game action. The bad board is H during the high score display but gives a slow pulsing H during the blank screen when it is supposed to show action. I have swapped the chips but it did not help. I don't understand WAIT enough to know what this means.
Also, there is a 8255AC-5 chip that is HIGH on pin 3-4 (PA0-PA1) on the working board but stays LOW except for a very quick blip to HIGH when it goes from the high score display to where the gameplay should be during the attract.
Short description - Wait pin shows a steady high rhythmic pulse.
Long description:
I have two Zaxxon boardsets. One with a working "A" board and one with a non-working "A" board. The bad board will display the high score table during attract mode but when it tries to show the game action during the attract it just displays a blank screen. I see that WAIT on the working board is HIGH during the high score display and is rapidly pulsing during the game action. The bad board is H during the high score display but gives a slow pulsing H during the blank screen when it is supposed to show action. I have swapped the chips but it did not help. I don't understand WAIT enough to know what this means.
Also, there is a 8255AC-5 chip that is HIGH on pin 3-4 (PA0-PA1) on the working board but stays LOW except for a very quick blip to HIGH when it goes from the high score display to where the gameplay should be during the attract.