blinddog
Well-known member
Stunt Cycle symptoms: The game would come up and start but the motorcycle would not move forward. There was a line of buses covering the bottom of the screen and the first player start button didn't light. I also found out later that the cycle image would break up going left and the bonus game setting were not always working.
--Bad 7400 @ N5: N5 controls the 566 that creates the speed pulses. N5 output was stuck high turning off the 566 and the motorcycle could not move forward
Now the motorcycle was moving but when it went off the screen it would appear in a random location and going a random direction also when the motorcycle was moving to the left the image broke up. The video was made after I replaced N4
--Bad 7474 @ N4: N4 is part of the circuit that causes the motorcycle to move down 32 lines and switch directions but without N4 it was getting random information
--bad 7400 @ B2: there are two shift register that load the cycle image then shift the image left or right. B2 tells the register when to load and when to shift. One of the B2 outputs was stuck and causing the bad graphics.
Now the motorcycle was getting to the bottom of the track correctly but there was still the full line of buses at the bottom where it crashed.
--Bad 7486 @ C8 and 7485 @ E6: E6 takes the score (number of buses jumped) and uses that to calculate how many buses to display. Because it was bad I guess nothing told the game to stop drawing the buses. C8 was a bad exclusive or gate which would have caused the input data to be wrong.
Now the game was playing correctly except the switch that controls when you get a bonus game was flaky and wouldn't always work and player one switch still wouldn't light up when you coin up
--bad 53137-1 @ F7: the 16 position switch was not working correctly. Replaced it with the a newer version 53137-5
--Bad MCR 101 @ Q18: replaced with NTE5400 so the bulb under the one player switch would get power
Everything is now working
--Bad 7400 @ N5: N5 controls the 566 that creates the speed pulses. N5 output was stuck high turning off the 566 and the motorcycle could not move forward
Now the motorcycle was moving but when it went off the screen it would appear in a random location and going a random direction also when the motorcycle was moving to the left the image broke up. The video was made after I replaced N4
--Bad 7474 @ N4: N4 is part of the circuit that causes the motorcycle to move down 32 lines and switch directions but without N4 it was getting random information
--bad 7400 @ B2: there are two shift register that load the cycle image then shift the image left or right. B2 tells the register when to load and when to shift. One of the B2 outputs was stuck and causing the bad graphics.
Now the motorcycle was getting to the bottom of the track correctly but there was still the full line of buses at the bottom where it crashed.
--Bad 7486 @ C8 and 7485 @ E6: E6 takes the score (number of buses jumped) and uses that to calculate how many buses to display. Because it was bad I guess nothing told the game to stop drawing the buses. C8 was a bad exclusive or gate which would have caused the input data to be wrong.
Now the game was playing correctly except the switch that controls when you get a bonus game was flaky and wouldn't always work and player one switch still wouldn't light up when you coin up
--bad 53137-1 @ F7: the 16 position switch was not working correctly. Replaced it with the a newer version 53137-5
--Bad MCR 101 @ Q18: replaced with NTE5400 so the bulb under the one player switch would get power
Everything is now working
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