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Thread: Capcom 1943 repair log

  1. #1
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    Capcom 1943 repair log

    I was waiting for an admin to create me an account on jammarcade.net but it doesn't seem to come...
    I got a non working 1943 board from fluxcore. First obvious thing to notice is +5V connectors were burnt on the JAMMA edge. Never a good sign. I checked for other burnt traces or components on the board and even blown capacitors but didn't find any. So it was time to power it... Nothing came on screen. One thing I always do in that case is checking if any IC is getting hot. And the sub Z80 (for sound) was. I replaced it but saw no improvement. I then started to check the main Z80 lines and the main RAM lines and while doing so I got some music. I replaced the main RAM and the game booted but with wrong text colors:

    DSCN4465.JPG

    I replaced two 273s at positions 5E and 5F and the game played fine. For 30mn...

    Then it started to reset every second, indicating the protection chip (i8751) has died. Unfortunately this chip is read-protected and hasn't been dumped. I had a look at the MAME file and discovered the protection was quite simple:

    Quote Originally Posted by MAME
    46 READ8_MEMBER(_1943_state::c1943_protection_r)
    47 {
    48 // The game crashes (through a jump to 0x8000) if the return value is not what it expects..
    With an hex editor I searched for C3 00 80 (JP 0x8000) in the program ROMs and found 3 locations. The game simply compares two registers (one coming from the protection mcu) if equal the game jumps relatively 0x11 addresses forward if not it clears some registers and jump (absolute) to 0x8000 (reset?). I replaced the cp b instruction (data coming from the protection chip being stored in b) by cp a (the data calculated by the main Z80 being stored in a). This correspond in hex by replacing 0xB8 by 0xBF. Now the patched game (only 3 bytes to modify) compares a with a so it's always equal. I burnt the patched code in a 27C256 and played the game to the end just to be sure everything was fine. With this patch the protection chip can be completely removed.
    [Note]The same method may be applicable to other Capcom Commando based games.[/Note]

    The day after I played the game again and after 15mn clouds in the background turned grey... This time I replaced the 273 at 13B and the game was fixed.
    I let the game running for few hours without any new issue. Finally!

    DSCN4464.JPG
    Last edited by Apocalypse; 05-05-2016 at 11:22 PM.
    Current SNK projects:
    - Samurai Spirits (Shodown) RPG English version for the NGCD:
    http://www.neo-geo.com/forums/showth...nch-to-English)
    - AES to MVS converter (plays AES games on MVS):
    http://www.neo-geo.com/forums/showth...-games-on-MVS)


  2. #2
    Choi's Barber
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    Nice work, especially with the ROM patch! Great game too.

  3. #3
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    Nice repair, now let's go down the rabbit hole further, what would have to be done to a 1943 board to convert it to run 1943 Kai?

  4. #4
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    Thanks guys.
    Quote Originally Posted by Westcb View Post
    what would have to be done to a 1943 board to convert it to run 1943 Kai?
    Only EPROM/PROM update:
    4K/5H/7F/12A/12D/13A/13D/14A/14D on the top board
    5F/6L/7C/7L/8C/8K/10A/10C/11A/11C/11F/11J/12A/12C/12F/12J/12L/12M/14A/14C/14F/14J/14K/14L on the bottom board
    Current SNK projects:
    - Samurai Spirits (Shodown) RPG English version for the NGCD:
    http://www.neo-geo.com/forums/showth...nch-to-English)
    - AES to MVS converter (plays AES games on MVS):
    http://www.neo-geo.com/forums/showth...-games-on-MVS)


  5. #5
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    Great work as always, so glad you got this working... and relatively simple fixes in the end too! Your ex-colleague will be chuffed
    There is no knowledge that is not power

  6. #6
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    Quote Originally Posted by fluxcore View Post
    Great work as always, so glad you got this working... and relatively simple fixes in the end too! Your ex-colleague will be chuffed
    I didn't find it that easy TBH but I agree the protection was pretty weak (luckily). I was so disappointed when the game committed suicide... I was about to put the board in the junk pile but couldn't give up so easily.
    BTW my friend's son played it few days ago and concluded it was way too hard
    Last edited by Apocalypse; 05-06-2016 at 06:26 AM.
    Current SNK projects:
    - Samurai Spirits (Shodown) RPG English version for the NGCD:
    http://www.neo-geo.com/forums/showth...nch-to-English)
    - AES to MVS converter (plays AES games on MVS):
    http://www.neo-geo.com/forums/showth...-games-on-MVS)


  7. #7
    Kula's Candy
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    Quote Originally Posted by Apocalypse View Post
    BTW my friend's son played it few days ago and concluded it was way too hard
    Then you explained the arcade business model, and how gamers were real gamers back in the day?
    There is no knowledge that is not power

  8. #8
    Sakura's Bank Manager
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    Thanks for posting your fix. I always enjoy reading through repair logs. This one sounded like a pretty hefty amount of investigation.

  9. #9
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    Quote Originally Posted by Apocalypse View Post
    Thanks guys.

    Only EPROM/PROM update:
    4K/5H/7F/12A/12D/13A/13D/14A/14D on the top board
    5F/6L/7C/7L/8C/8K/10A/10C/11A/11C/11F/11J/12A/12C/12F/12J/12L/12M/14A/14C/14F/14J/14K/14L on the bottom board
    Piggybacking on this, to convert Commando hardware to any other game, barring CPU clock differences is it only EPROM swapping, or is there unique protection per game that needs to be bypassed (I think no?)?

  10. #10
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    Quote Originally Posted by fluxcore View Post
    Then you explained the arcade business model, and how gamers were real gamers back in the day?
    Hardcore gaming 4 life!

    Quote Originally Posted by DanAdamKOF View Post
    Piggybacking on this, to convert Commando hardware to any other game, barring CPU clock differences is it only EPROM swapping, or is there unique protection per game that needs to be bypassed (I think no?)?
    In the case of 1943 and 1943 Kai, hardware is identical (even clock speeds), only EPROMs/PROMs need to be swapped, the protection chips are identical.
    The protection chips are different between other commando hardware based games but can be bypassed with the same method.
    Current SNK projects:
    - Samurai Spirits (Shodown) RPG English version for the NGCD:
    http://www.neo-geo.com/forums/showth...nch-to-English)
    - AES to MVS converter (plays AES games on MVS):
    http://www.neo-geo.com/forums/showth...-games-on-MVS)


  11. #11
    Kyo's Flame
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    Thanks for the info!

  12. #12
    Kuroko's Training Dummy

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    really nice repair, especially the ROM patching part ! Thanks for posting this !

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