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NeoGeo 6 Slot Board Repairlog

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  • NeoGeo 6 Slot Board Repairlog

    Had Scratcha's NeoGeo 6 Slot on the bench today, fricken massive thing but unwell, it booted up giving this RAM error..



    These error messages can be read like this...

    ..the board tried to write XXYY to the two ram chips in the memory stack at the location stated, XX to the low addressed chip and YY to the high addressed chip (or perhaps the otherway round, it doesn't really matter). So from the above error you can infer that both chips are faulty, but only if you assume that its not a problem in the RAM controller logic, which is also possible. NeoGeo boards have an onboard battery that leaks corrosive shite when they age and the tracks on these boards are microscopic, they don't like the battery acid and they just corrode away to dust, track damage is a common problem.

    The second problem with NeoGeo boards is finding which RAM chips the error message is talking about, half the problem there are so many board variants so chip location advice you find for a 2 slot board is not much use for a 4, or even a 6.

    Anyway - with a bit of googling I found that the address the error message refers to determines which chip type is considered faulty.

    Address 0000 means the board thinks the surface mount 62256 RAM chips are the problem, if that was the error for this board I would consider it scrap, or a boat anchor, its big enough.

    Thankfully this error was at address 8000 which meant it was the Sony CKX5814 chip pair in the top right-hand corner of the lower board. It also helped that my logic probe showed the lower of the pair had its I/O lines D3 to D7 stuck low. The other chip looked healthy based on pin activity alone.




    Desoldered this chip and tested on my eprom burner/chip tester and it showed up as faulty. Comparing the datasheets for this chip and the chips I had on my scrap boards showed I could use bog standard 6116 chips as replacements, so I dropped one in and fired the board back up to see what the error message would give.



    So now the board is writing 00 to one chip and getting 00 back, but still writing 00 but getting 04 back from the second chip in the pair.

    Replaced the second chip (which also tested as faulty) and the board booted to the crosshatch screen, which is what a NeoGeo board should do without a game cart inserted, or in this case without the cart interface board connected.



    Connected it all back up, plugged it into my cab and after a bit of faff seating and reseating the carts I got it to work perfectly.



    Anyone know a good method for cleaning the contacts in the cart slots? The egde of the ROM cart is easy enough, but the contacts on the slot may be a pain.

    Oh and one of the two carts gives no sound, I assume it has a very dead EPROM inside, but thats for another day.

    One final thing I should do to this is to rehouse the battery, its just starting to leak but has only reached the leg of a resistor at the moment, should really fit flying leads and house the battery away from the PCB, otherwise this board is living on borrowed time.
    Sic transit gloria Atari!

  • #2
    Thats awesome mate.... It is a big sucker hey.... best I bring some beer on the next visit.. Thanks buddy..

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    • #3
      Anyone know a good method for cleaning the contacts in the cart slots?

      I use white paper, sliding it from one end to the other till the paper no longer gets dirt on it.
      WANTED

      Another Holiday
      .

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      • #4
        Womble is a champ, well done. Scratcha no excuses now for not having that cab fired up soon.

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        • #5
          Spot on mate, got the 100-1 Board ready to slip straight in......

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          • #6
            I removed the battery from the board, another 6 months to a year and it would have made a real mess, it had already eaten through the upper layer of the board down to the copper ground plane in places.



            Scraped away all the crud and neutralised the alkaline muck then gave it a clean up with PCB cleaner. The board works fine without its battery, Gamedude reckons the battery is only for book-keeping functions (ie how much money has been taken, length of games, etc etc).

            Gave the slots a go over with the paper trick and it seems to have worked, much more stable, originally the slightest touch on the cart would put lines through the gfx and or crash the board - crap connections clearly.
            Last edited by Womble; 21st May 2009, 11:46 AM.
            Sic transit gloria Atari!

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            • #7
              I use a similar method for cleaning my cartridge connectors, however I tear a bit of cardboard off something (manilla folder, etc), fold it over an old credit card, spray a bit of isopropyl on it and insert/remove it a few times.

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              • #8
                Originally posted by humpalot View Post
                Anyone know a good method for cleaning the contacts in the cart slots?

                I use white paper, sliding it from one end to the other till the paper no longer gets dirt on it.
                I swear by the old tooth brush method using some decent contact cleaner (non residue CRC is good)
                http://www.hardmvs.com/html/slotCleaning.htm

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                • #9
                  My NeoGeo 6 slot doesn't even boot to crosshatch.Please Help!

                  I just received a Neo Geo 6 slot and it doesn't boot to the crosshatch screen. My monitor just displays red blocks.Please Help.
                  Photos:
                  http://i1272.photobucket.com/albums/...psc2a442cb.jpg
                  http://i1272.photobucket.com/albums/...ps9c7ea632.jpg
                  http://i1272.photobucket.com/albums/...ps542d7de0.jpg
                  http://i1272.photobucket.com/albums/...ps60dafe93.jpg
                  http://i1272.photobucket.com/albums/...pse7531ebf.jpg
                  Last edited by misschivous; 27th February 2013, 09:54 AM.

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                  • #10
                    Could be bad RAM, but my money would be on track rot, possibly caused by a leaking battery on the lower board.
                    Sic transit gloria Atari!

                    Comment


                    • #11
                      Hey Womble,
                      You mentioned that you had a cart that had no sound and you suspected the rom. Did you end up fixing that one? I have a puzzle bubble cart with no sound also. Would be good to fix that one up.

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                      • #12
                        Nah, haven't even looked at it, tended to shy away from NG stuff as its too much of a pita to repair. Its a bootleg multi cart so even if the ROM is bad I doubt I could find anything to replace it with.

                        First thing to try would be to dissemble the cart and polish the contacts on both PCBs.
                        Sic transit gloria Atari!

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                        • #13
                          Done all of that already. Checked for bad solder or any visible signs of damage. Boards look clean and perfect.
                          If replacing the roms could fix this I may give that one a hit and see.

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                          • #14
                            If other carts work fine on the board then it probably is the audio ROM board in the cart. PB is a small game so it is not likely to be a bad upper address track on the main board that allows smaller games to work but not larger ones. Desolder the ROM and try and dump it would be the next step.
                            Sic transit gloria Atari!

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                            • #15
                              Originally posted by mamejay View Post
                              Hey Womble,
                              You mentioned that you had a cart that had no sound and you suspected the rom. Did you end up fixing that one? I have a puzzle bubble cart with no sound also. Would be good to fix that one up.
                              I can fix it for you if you get stuck, I did one just last week.

                              Puzzle Bobble is a tricky one with the V ROMs for a couple reasons. First reason being if its a genuine SNK original cart, ill have some ROM chips from Power Spikes 2 in there ( number 068, V1 and V2 will be, as will C1, C2, C3, and C4 )
                              Originally posted by Womble View Post
                              If other carts work fine on the board then it probably is the audio ROM board in the cart. PB is a small game so it is not likely to be a bad upper address track on the main board that allows smaller games to work but not larger ones. Desolder the ROM and try and dump it would be the next step.
                              There is two V ROMs ( sounds ) in Puzzle Bobble, and also the sound controller ROM is M1 on the CHA board. M1 on this cart is a common failure, and if it goes, will cause no sound.
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