Stunt Cycle repair log

blinddog

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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

 
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Awesome... thanks for sharing.
I really love reading repair logs and how people figure things out. Plus it always helps as a reference.

cheers
/Tim
p.s. Stunt Cycle is a cool B/W game... I remember playing it at Aladdin's Castle.
 
Very cool log. Pre-CPU games intrigue me. I think I'm going to pull up the schematics and try following along more closely...
 
Thank you for taking the time to document and post this. Good stuff. I know you love these old games like I do, just wish I had more room.

Also, I don't know if I ever messaged you but it was nice meeting you at SanTe's back in June and had a really good time hanging out. Hopefully next time I come up I get the chance to see your collection.

Rob
 
Nice job Matt! It looks like you're getting good at board repairs. - Barry

Well it seems every time I start to think that the next board comes and knocks me down a couple of pegs. Been fighting a Gun Fight PCB lately and it seems to be winning.

Also, I don't know if I ever messaged you but it was nice meeting you at SanTe's back in June and had a really good time hanging out. Hopefully next time I come up I get the chance to see your collection.

Rob

Yeah next time you make it over this way let me know. I'll have an arcade get together over at my place and you can get your fill of 70's games.
 
Well it seems every time I start to think that the next board comes and knocks me down a couple of pegs. Been fighting a Gun Fight PCB lately and it seems to be winning.



Yeah next time you make it over this way let me know. I'll have an arcade get together over at my place and you can get your fill of 70's games.

You have an awesome collection blinddog!
 
Another stunt cycle fix

Thought I add another fix to my Stunt Cycle log. I didn't take a video of this one sorry.

Symptom: The motorcycle would not reset to start position after a successful jump. It would continue off the right side of the screen drop 32 lines making it appear back at the very top of the screen moving left. It would continue dropping and switching directions until it hit the buses or the bike flipped and then it would finally reset to the start position. The crowd cheer also continued until the bike reset. The score would not advance

It turned out M5 (7410) a triple input nand gate was bad and the end of track signal was not getting to N6 to reset the bike to start position
 
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