jkoolpe
Well-known member
Hey all!
I'm working on a Major Havoc board for a friend.
Symptoms: No activity at all when powered up in my otherwise fully working Major Havoc upright (a Space Duel conversion). Test mode also completely non-functional.
Using my o-scope, I see that the main reset line (called the reset alpha in the schematics) is stuck in a repeating high/low mode. In other words, the horizontal line on my scope's screen for the legs on the relevant chips (the 6502 alpha microprocessor and some LS244 and LS245 chips nearby) is alternating between hi and low repeatedly so the game seems to be stuck in a reset mode of sorts.
I changed one of the LS244 chips at location 2P, and also swapped the 6502 microprocessor chips (there are 2) for a new ones to no avail.
I'm thinking to try the LM324 chip that the schematics also show as part of the reset function.
Anyone have any other ideas for me?
Thanks!
Jon
I'm working on a Major Havoc board for a friend.
Symptoms: No activity at all when powered up in my otherwise fully working Major Havoc upright (a Space Duel conversion). Test mode also completely non-functional.
Using my o-scope, I see that the main reset line (called the reset alpha in the schematics) is stuck in a repeating high/low mode. In other words, the horizontal line on my scope's screen for the legs on the relevant chips (the 6502 alpha microprocessor and some LS244 and LS245 chips nearby) is alternating between hi and low repeatedly so the game seems to be stuck in a reset mode of sorts.
I changed one of the LS244 chips at location 2P, and also swapped the 6502 microprocessor chips (there are 2) for a new ones to no avail.
I'm thinking to try the LM324 chip that the schematics also show as part of the reset function.
Anyone have any other ideas for me?
Thanks!
Jon