Ultimate Mortal Kombat 3 pcb start buttons not registering

kidrivers

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Ultimate Mortal Kombat 3 pcb start buttons not registering

So i went to play UMK3 today and i can't get it to accept the start button presses. I tried it in 2 cabinets that have other Mk games in them with the same result. the pcb goes through it's boot check just fine. I went into the diagnostics and all buttons work except player 1 & 2 start. The traces look good where the jamma harness plugs in, and this has been in the same cabinet and not moved around for over a year. Any ideas????? thanks
 
Simple and easy thing to start with...(pun intended). The start buttons are missing the grounds or the grounds aren't being seen by the board. Take a wire, attach it to the jamma harness's ground wires, and touch it to the start button wires on the jamma harness at the edge connector. If the game still does not start, it's a board issue. If they do, it's a wiring issue.
 
i'll give both suggestions a try and report back. i don't think it is the cabinet though because i tried it in 2 cabs (both MK) and they both work fine but the UMK3 doesn't. Thanks guys!!!
 
Simple and easy thing to start with...(pun intended). The start buttons are missing the grounds or the grounds aren't being seen by the board. Take a wire, attach it to the jamma harness's ground wires, and touch it to the start button wires on the jamma harness at the edge connector. If the game still does not start, it's a board issue. If they do, it's a wiring issue.

sounds like a board issue to me.

Ctozzi took the words out of my mouth, finally the word is getting out.


edit: any touching pins on the solder side by any chance? and have you done anything to the board recently before this started? (ex. rom upgrades or accidental leaning on while fixing something else) i know you did mention the board hasn't been moved but i gotta ask.
 
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Okay, i cleaned the edge connector with no luck. I then plugged it in booted it up and took a ground wire and put it to the jamma board/jamma harness like zenomorp said and it worked. I am puzzled because i can switch to MK1 and it works perfectly. I have done this in 2 cabinets with the same result. What exactly does this mean??? How is MK1 and MK2 getting the ground from the same plug MK3 isn't?? Thanks guys
 
At least we have now eliminated the board as the problem. That's good. Follow the ground coming off your start buttons and see where they lead. It/they should be running to one or the other end of the Jamma harness connector. If all else fails, run a new ground from any of the other working buttons to the start buttons and you should have this problem licked.
 
crazy 2 cabinets with the same exact problem only with 1 board... very strange.

i would equally like to know the reasoning behind this.
 
i'll try a new ground wire tomorrow and let you guys know what happened. i am thinking that maybe i should re-tin the player 1 and 2 start leads on the board. They don't look bad, but maybe they are worn enough that the jamma harness isnt making good connection there. I'll try the new ground 1st though. thanks again guys and talk to you tomorrow.
 
All right, i don't know what is going on but i turned on the game again and tried a different ground wire and nothing... i used the other ground that worked the last time and still nothing. Also when i booted it up this time there was some graphical glitches, like the words were all run together/static-y (is that a word?) across the top of the screen, but all the roms check out fine. i rebooted and it was all good. So i don't know what to do, but i am sure it is a board problem now... any ideas???? Thanks
 
Re-seat (if you have a PLCC puller), or press down to firmly seat (if you don't) the U45 and U47 PLCC graphics chips. They are the ones in the brown square holders.
 
Okay, the unthinkable has happened....it worked!! I don't have a puller so i just pressed the chips down. I didn't feel any movement on either chip, but when i plugged it in it worked perfectly. I did have to replace the CMOS battery all of a sudden.... but whatever. Hopefully it won't act up again but i do appreciate all the help you guys gave, thanks and i hope i can repay the favor sometime. Thanks again.
 
Okay, the unthinkable has happened....it worked!! I don't have a puller so i just pressed the chips down. I didn't feel any movement on either chip, but when i plugged it in it worked perfectly. I did have to replace the CMOS battery all of a sudden.... but whatever. Hopefully it won't act up again but i do appreciate all the help you guys gave, thanks and i hope i can repay the favor sometime. Thanks again.

Awesome! Those chips play a much bigger role than just graphics. They are always a last resort for me when troubleshooting. Whenever I get a Wolf Unit that has issues, I always reseat/replace/temp install new ones to see if the originals are bad. Sometimes I get lucky. Sometimes I don't. Usually the latter. Glad to have been of service!
 
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