Mortal kombat 2 - tests okay then resets

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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
 
I'm thinking it may be a battery issue? Because I have 2 MK 1 boards. 1 does the same thing and unless I service credit the game or insert coin to make it go to the main screen. It just keeps resetting itself. Then when I go to the player select screen I have a graphic glitch. Otherwise it works just fine.

The battery on that one looks in bad condition and I'm thinking it's about to go hence the problems and why I thinks it's the battery. My other board just won't boot, but the red lights come on.

Can you at least credit the game and start it? Or go into dip switch settings?
 
This board doesn't have a battery, but I thought that it was still possible to get into the game with no battery?

DIP switch test setting won't take it into the main test mode. :(
 
the board should have a battery, not sure what its for other than saving high scores and menu options, but cant hurt?

also i can only get into my menu with a dipswitch, my service and volume switches do not work, there not wired up.

the dipswitch is one of the first or last on one of the banks, I dont know numbers or which bank (theres only 2) but its one on the end
 
I've been waiting for weeks for a friggin JAMMA game question. I hate this place with all these stupid "classic" games.

resets can be caused by a couple of ways...

either your +5 voltage is too low, or you're looking at a program rom issue.

if you can probe a rom or other IC on the main board and get 5.10 volts, you're looking good. when you start dipping below 4.9, you're looking at either a an older problematic power supply, your JAMMA contacts are dirty on the 5 volt lines, or something stupid like the wires being 40 feet long like in my MK2 cab and it's just creating a lot of resistance along the way. if you pop the board out and go over the JAMMA edge with a pencil eraser you'll probably find a lot of shit coming off. always be mindful not to get the rubber trimmings somewhere on the board though, I always just wipe it away with my finger.

the 2 game roms, if they've formed corrosion on the chip legs, can cause your problem as well. I only speak of this from personal experience on my MK2, which I inevitably wound up sanding the chip legs (with sandpaper) and it made my "sound IRQ not detected/baby crying" or random reset problems go away.

if you have further questions feel free to PM me. good luck!
 
Thanks, but voltages are fine, EPROMs are fine. :)

Just to reiterate - it boots, displays that all of the ROMs and RAMs are fine (ie all green), goes to a blank screen with 'Revision 2.1' at the top, then reboots.
 
if it's anything like nba jam (which it is). the battery should fix your issue.

always good to take mecha's advice his advice is always spot on. but since you've checked all that, my dollar is on the battery. keep us updated!
 
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?
 
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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.

ohhhhh, are you skewling from bangkok again? :D

come to think of it i'd like to change my bet to agree with mecha and zeno, from what i remember with other peoples NBA Jam boards they would get into the game fine and play but then all of a sudden randomly reset once the game ended i believe (also when your score would be saved).

regardless if you already got/ordered a battery, it's good to change out (or have one if you didn't already). that will atleast tell us if the battery was the issue for some reason anyways.
 
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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.
 
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.
 
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.
 
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.

damn dust bunnies make their homes in the worst places sometimes.
 
My MKII board had a bad battery for a while. It would show a CMOS error at start up, and tell you to press "any button" to continue. Once you did that, the game worked fine.
I have since replaced the battery (Radio Shack) and the CMOS error has subsided.

On a related note, I just hooked up my Total Carnage board in a JAMMA cab, and it is resetting at random points after the game is running. It doesn't reset all the way back to the test screen though, just back to where it shows the revision. I will check voltages later today. This is the same cab that has run Tekken 2/3 for years with no issues.
 
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