Mortal Kombat Bootleg PCBs

Discussion in 'Arcade and Supergun' started by MottZilla, Mar 21, 2013.

  1. MottZilla

    MottZilla Guardian of the Forum

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    I posted awhile back about my bootleg Mortal Kombat 1 which seemed to suffer a rather minor video problem, missing pixels in the sprites. I didn't really pursue fixing it but now I think it might be the ROMs containing the bitmaps were going bad. But now the board doesn't run at all so I can't test it. But besides wondering what is wrong with it now, the bootleg I have I haven't seen any pictures of so I thought I would take a few to share. Anyone else have one of these? I need to get the T-Unit 5.0 official board someday but it would be nice to get this bootleg of the Y-Unit version working again. It did work and play ok with sound before. But I have no clue what might have happened since then. EPROM failure is my only guess. Any tips? Besides buying another board.

    mk1b1.jpg mk1b2.jpg

    There are close up pictures of higher quality in an archive located here.

    Update: I've been looking around and actually there are pictures of a similar board. There is one that this Turbo hack is on and someone mentioned graphics glitches if they 5v rail isn't slightly over 5.0v. Maybe that was my issue back before the board developed a new unknown problem.

    Update 2: I dumped the Program EPROMs and they are intact and 100% match official Revision 3.0. Still no clue as to why my board won't work. It just does nothing on power up. Nothing on screen, nothing through the speaker.
     
    Last edited: Mar 22, 2013
  2. MottZilla

    MottZilla Guardian of the Forum

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    Well, removing the top board causes a rolling video bitmap pattern! So I'm wondering if it has to do with a bad connection to the top board or something like that. If anyone has any ideas I'd like to heard them. But without the top board atleast something displays.
     
  3. ASSEMbler_archived

    ASSEMbler_archived Pillar of the Community ****

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    I wish you had posted HD of the pics so I can see the TI ic on there.
     
  4. MottZilla

    MottZilla Guardian of the Forum

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    Did you download the archive with more pictures? There are close ups. One is the TI TMS CPU, the other is a TI FPGA on the top board. Good news, the boards runs again, but it resets/crashes before getting into the game and at other times. But it is running sort of. I think its related to the top board connection or a bad component. The Self Test tells me RAM chip U5 is bad. But U5 is the official board. It also claims I think U99 custom chip is bad. The game as I said is still very flakey but it shows signs that is should be able to function 100%.

    Update: I've read the U99 bad custom chip is normal on bootlegs. Not sure about the bad ram thing. Right now the board doesn't want to run again. No idea why exactly. Might be what appear to be cold joints of the FPGA chip on the smaller top board. Wiggling the board around got it working before.
     
    Last edited: Mar 23, 2013
  5. MottZilla

    MottZilla Guardian of the Forum

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    So I resoldered a few suspect joints on the daughter board but it didn't seem to help. But I did discover that the main board flexing allows it to work partially again. I'm guessing this means one of two things. Bad solder joint somewhere, or worse, a crack in the board somewhere? I can pretty reliably get the board to boot up and run to the point that Kano's BIO appears and sometimes the part with the character strips scrolling on each side. But it tends to crash/reset on the character select and if not there it's likely to happen on the ladder screen and rarely if ever do I see the first battle screen. Any good tips?
     
  6. ASSEMbler_archived

    ASSEMbler_archived Pillar of the Community ****

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    More than likely you have a cracked trace if it's a bootleg. check continuity of the pins in the connector? lots of work for sure...
     
    Last edited: Mar 25, 2013
  7. MottZilla

    MottZilla Guardian of the Forum

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    It is a bootleg, so you suggest just checking every single trace pretty much? Though if it's cracked and sometimes makes contact but not always I'd think continuity alone wouldn't be reliable for a test, because when i test it, it might be bending in favor of the crack.

    I've been resoldering all sorts of joints tonight and I think it has improved but it's not right yet. I did check the continuity of the daughterboard connectors and they are OK. It's something on the main board. Probably could be just one of the many little 74 series ICs.
     
  8. MottZilla

    MottZilla Guardian of the Forum

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    Well, the game works alot better. The last things I did was touched up maybe 2 solder points but the main thing I did was removed the protection IC (its a PLD made by Intel) and then reseated it. So far (cross your fingers) it's working much better. Still graphics issues that I've read are likely related to low 5v rail voltage. But the game hasn't crashed and I made it to Match #8 (first endurance round) without any crashes. I lost because I don't have the extra 2 buttons hooked up right now. But atleast it seems stable.

    So it seems most likely the problem was with the PLD chip in the middle having some issue. When removed the system won't come out of reset or something like that I think. But I'll post if it starts acting up again incase someone else has a bootleg like this having random reset issues so they can have some suggestions to try fixing it.

    Now I just need to see about the low voltage. One time I tested it was at 4.4v or something when under load.

    Update: I was looking at the extra buttons, these guys have it all messed up. Jamma Edge Player 1 button 4 belongs to player 2! P1 button 5 does belong to Player 1. I located the IC they hook up to and I figure I'll just bend the legs up. I'll double check, but this is messed up that they didnt even respect which side was player 1 and which was player 2.

    Update: My solution for the extra buttons was to bend the pins on the 74*245 chip since it was in a socket and easy to take out. The inputs run to the wrong jamma edge pins so disconnecting them was definitely needed. When I get a chance I suppose I should solder some wires to the pins, figure out something for connecting it to my Supergun. For anyone else with this bootleg board this is a picture of the IC and which pins. It's very close to the two DIP switch blocks.

    extrabuttons.jpg
     
    Last edited: Mar 27, 2013
  9. MottZilla

    MottZilla Guardian of the Forum

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    I got a reply from someone that owns the same type of bootleg as I do and he described a similar graphics problem to what I have being related to low 5v rail voltage. He said raising his 5v rail to 5.16v eliminated the issue. I've been advised that my two choices are get a better PSU that is adjustable on the 5v rail, or possibly replacing some or all of the 74LS series discrete logic chips with 74HCT series chips which draw less current. Replacing the chips since only a few are socketed would be quite alot of work. But if then I could use the same PSU that would be nice. But I suppose if other boards might have similar problems with wanting more out of the 5v rail then it's back to the PSU.

    update: I tested the 5v line under load with the top board removed that has around 60-70 chips on it. The voltage increased to 4.7v. So I'm doubting that replacing all those chips with more power efficient ones would help enough. It seems a better power supply is definitely required. I guess that'll get me to work on my Supergun some more. Still should paint it one of these days.
     
    Last edited: Mar 27, 2013
  10. MottZilla

    MottZilla Guardian of the Forum

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    Just for reference, I tested the board with an Arcade PSU that has an adjustable +5v rail. Increased voltage decreased some of the graphics glitches but even at measured 5.2v and 5.3v it never fully went away. Maybe someday I'll figure out what the deal is.
     
  11. splith

    splith Resolute Member

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    What's the power going into, a regulator on the board, resistors or straight to the chips or what? Sounds like something is undervolted, check the voltages of the power pins on the various GFX-related chips?
     
  12. MottZilla

    MottZilla Guardian of the Forum

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    There are pictures in the very first post. There is a link to more pictures too. mkbootleg.rar

    There are some caps and a transistor or something near the edge connector. Are you suggesting maybe the transistor is shot?
     
  13. ac3

    ac3 Member

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    A few years too late I know, just thought I'd mention I have the same board with the same graphics issues. Like you said adjusting the 5v helps (as is common with bootlegs) but doesn't fix it completely. I suspect a bad dram or two, I see this a lot with cps1 boards. Also I hope you removed the battery it's started to leak in your photos and that was three years ago.
     
  14. MottZilla

    MottZilla Guardian of the Forum

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    I can't remember if I removed the battery. I eventually stopped worrying about it figuring if I ever get serious about it I might pickup an official board set. Although they are more expensive than they used to be. Last I tried the board I'm not even sure it works at all.
     

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