Scucci
Well-known member
I'm about to shred this board... it's killing me.
/CE and /OE on 2 of the EPROMs are acting funny. I traced those back to a 74138... replaced it. It's acting exactly the same. The only thing before that 138 is the 6809 CPU. I've replaced it with 3 different ones. All 3 act exactly the same.
I'm not sure if the CPU isn't getting enough time to run through a cycle to check them all and they're just staying high (although one is pulsing high... no low... just float, high, float, high... no activity on the low LED at all on my probe).
The only think I can figure is it's the CPU... but what would make both 01 of them (the 6809 AND the Z80) hump the board like that?
I think the crystal MIGHT be faulty... but on EVERY other Konami 36 pin board, when they crystal goes out it just screws up or takes out the audio... that's it.
The ONLY other thing I see in there that's acting goofy is the 555... considering it's a timer... there's no pulsing going on there, but I can't follow the circuit enough to figure out if that's by design (for whatever reason) or if it's seized on me.
There's a Mikie board at work, so I guess I'll just have to check that side by side with mine... but does anyone have any other suggestions in case that doesn't work out?
... and in case I can't get around to it... and you have easy access to a Mikie board... and a logic probe... and 5 mins... and a heart of gold (or tin... either or... just some metal of some sort)... is there ANY chance you can check that 555 for me and see WTH it's doing? It's a 6B, the little guy.
/CE and /OE on 2 of the EPROMs are acting funny. I traced those back to a 74138... replaced it. It's acting exactly the same. The only thing before that 138 is the 6809 CPU. I've replaced it with 3 different ones. All 3 act exactly the same.
I'm not sure if the CPU isn't getting enough time to run through a cycle to check them all and they're just staying high (although one is pulsing high... no low... just float, high, float, high... no activity on the low LED at all on my probe).
The only think I can figure is it's the CPU... but what would make both 01 of them (the 6809 AND the Z80) hump the board like that?
I think the crystal MIGHT be faulty... but on EVERY other Konami 36 pin board, when they crystal goes out it just screws up or takes out the audio... that's it.
The ONLY other thing I see in there that's acting goofy is the 555... considering it's a timer... there's no pulsing going on there, but I can't follow the circuit enough to figure out if that's by design (for whatever reason) or if it's seized on me.
There's a Mikie board at work, so I guess I'll just have to check that side by side with mine... but does anyone have any other suggestions in case that doesn't work out?
... and in case I can't get around to it... and you have easy access to a Mikie board... and a logic probe... and 5 mins... and a heart of gold (or tin... either or... just some metal of some sort)... is there ANY chance you can check that 555 for me and see WTH it's doing? It's a 6B, the little guy.
