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Can't figure this out - original Mortal Kombat 2 PCB, runs through the initial tests okay, no errors reported, then resets.
Any ideas please?
Thanks
Any ideas please?
Thanks
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Had this exact issue with an MK1 pcb. Turned out to be a voltage issue. The battery is for nothing but CMOS settings in my experience. The battery is only to store CMOS info. I have used boards many times before that worked perfectly with no CMOS battery. When I tuned up the voltage on the power supply, the MK1 started working great.
My money's on voltage issue. Of course, the other experts here could be right about the program roms being bad, but they usually will register as bad on the boot up test. Sometimes they don't though. Increase your voltage a little and see what that does. If nothing, try re-seating the program roms.
Had this exact issue with an MK1 pcb. Turned out to be a voltage issue. MK boards are VERY picky about voltage. Try running 5.20vdc instead of 5vdc. Different power supplies will offer different amps at different voltages, so one might register as putting out 5 volts, but at a lower amperage that another. The battery is for nothing but CMOS settings in my experience. The battery is only to store CMOS info. I have used boards many times before that worked perfectly with no CMOS battery. When I tuned up the voltage on the power supply, the MK1 started working great.
My money's on voltage issue. Of course, the other experts here could be right about the program roms being bad, but they usually will register as bad on the boot up test. Sometimes they don't though. Increase your voltage a little and see what that does. If nothing, try re-seating the program roms.
What the MK1 did was go through the boot sequence, all roms green, sound test "tone", the "Midway Presents.....Mortal Kombat" would appear, then the board would reset. Is this a new board or one you've had for a while?
Voltage issues were my first thought, but no go (high or low). Relevant EPROMs also all verified okay in my programmer and also swapped in good ones from another board, but still no luck.
Continuity on program EPROM sockets is good.
I'm currently wondering if it's a logic chip failure, might have to do some prodding with my 'scope and logic probe when time allows. Too tired right now.
Ok. If this is a board you recently acquired, I would check the bottom of the board to make sure none of the socket feet are bent over touching each other. That has been known to cause some issues also.
ahoy yes, some people take the mounting feet off the boards, lay them on a flat surface, and then they bend over and touch each other. Williams/Midway for whatever reason always left their pins very long. you'll have to inspect the entire board, then use a little precision flathead to bend the pins up and use electronic shears (or snips as I call them) and trim the excess off.
I acquired a MK T-unit board in a "non-working" condition, it was actually a converted MK2 board with the memory expansion pulled off and all that.. the game played perfectly fine until it hit the Game Over screen, and then on the high score screen, it was scrambled up, and that's when the game would constantly reset, even after entirely cycling power.
after fucking with it for awhile, on a hunch I just blew onto the CPU and some fuzz came out, and went back to playing the game again and never got it to reset again after that.