blinddog
Well-known member
PCB: Kee Games Super bug
Symptoms: The board had the picture of the car in the middle of the screen but garbage was scrolling across the screen (see Pic)
Steps:
Because I was seeing the car on the screen I assumed the CPU was working, turns out that assumption was wrong. that error had me looking in the timing and playfield section for a bit until I figured out that the car image is placed were it is by the timing not the CPU.
Starting over fresh I checked the timing again and it was good. Then I moved to the CPU and saw that none of the address lines were moving.
I looked at the reset line next and it was stuck low and pushing the reset switch on the board didn't make a change at the cpu. There is a 7496 (shift register) that will kick the cpu reset if the code takes to long or if you hit the reset button. I figured that was bad.
I replaced the 7496 at D4 and the board came back to life. There was no other issues.
Repair: replaced 7496 at D4
Symptoms: The board had the picture of the car in the middle of the screen but garbage was scrolling across the screen (see Pic)
Steps:
Because I was seeing the car on the screen I assumed the CPU was working, turns out that assumption was wrong. that error had me looking in the timing and playfield section for a bit until I figured out that the car image is placed were it is by the timing not the CPU.
Starting over fresh I checked the timing again and it was good. Then I moved to the CPU and saw that none of the address lines were moving.
I looked at the reset line next and it was stuck low and pushing the reset switch on the board didn't make a change at the cpu. There is a 7496 (shift register) that will kick the cpu reset if the code takes to long or if you hit the reset button. I figured that was bad.
I replaced the 7496 at D4 and the board came back to life. There was no other issues.
Repair: replaced 7496 at D4



