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Thread: Mv1b1 color ram bank0 error. Can anything be done - has Neo-grc2

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    Mv1b1 color ram bank0 error. Can anything be done - has Neo-grc2

    Hi Guys,
    First post here

    I have a Neo single slot MV1b1 (1998). It was running well for a few games than it crapped the bed on me and threw up a error message upon boot : Color Ram
    Ram Bank0 Error. I read on the neo wiki page that the color ram is incorporated within the Neo-Grc2-F Custom chip and that any color ram issues are bad news (unrepairable). Regardless of this i tried swapping the ram chips "Ram 5" and ''ram 6'' as they connected to the grc2 with backup rams to see if the problem would move with the chips, but unfortunately not. I tried swapping the 74ls273's between each other to no change. I tried reflowing the Grc2 and fixed anything a little suspect like dirt and corrosion to no change.
    Is there anything that can be done to fix this board short of finding a donor Grc-2?

    now there maybe a clue in the error message itself to help narrow down the issue.
    the error messages comes up with the following-

    write 0614 read 0714 ( second bit is one ahead of what was written)
    So In binary number 6 is written as 0110 but read as Number 7 which = 0111 in binary - so last bit is stuck high.

    another example;
    write 00f2 read 01f2 ( second bit is one ahead of what was written)
    So In binary number 0 is written as 0000 but read as Number 1 which = 0001 in binary - so last bit is stuck high.

    another example;
    write 0AA2 read 0BA2 ( second bit is one ahead of what was written)
    So In binary Letter "A'' is written as 1010 but read as letter "B'" which = 1011 in binary - so last bit is stuck high yet again. this is the same upon a heap of reboots.

    So if the problem can not be solved as the custom is bad - can i tie that last bit to ground so it will pass the boot tests and if so which leg of grc-2 custom is it?. the boot tests seems to require that last bit to be a low 95% of the time the other 5% of the time it boots as it must be asking for a high on the last bit.
    I know this will mean some colors will be wrong but at this point its better then nothing. if i was to tie this pin to ground would it need to be through a resistor so effectively its not a straight ground short?
    I will attach some pics.
    Thank you for any help.

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    That should be the pics attached. Also i'm unable to fit a diagnostic rom as the rom is SMD. I am on the waiting list for a neo bios masta adaptor pcb when more come in stock.

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    what is installed bios?

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    Quote Originally Posted by pier View Post
    what is installed bios?
    STD bios as it’s smd and I don’t have a adaptor as per above post cheers

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    Quote Originally Posted by Adzy83 View Post
    STD bios as it’s smd and I don’t have a adaptor as per above post cheers
    install unibios because with default configuration it skip hw test during boot. it could be also useful to use diagn bios to test it.

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    Quote Originally Posted by pier View Post
    install unibios because with default configuration it skip hw test during boot. it could be also useful to use diagn bios to test it.
    Yeah I think Iím gonna need to solder the dip bios to the board. Maybe someone on here has a adaptor that they can sell me as they are out of stock.

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    I have several prototype VMC NeoBiosMastas for sale. The function the same as the production model but have a few manually routed wires.

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    Quote Originally Posted by shadowkn55 View Post
    I have several prototype VMC NeoBiosMastas for sale. The function the same as the production model but have a few manually routed wires.
    Awesome mate I can rout a few wires. Iíll see if I can pm you so we can sort out a deal

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    Quote Originally Posted by Adzy83 View Post
    Yeah I think Iím gonna need to solder the dip bios to the board. Maybe someone on here has a adaptor that they can sell me as they are out of stock.
    Great news soldered one the UniBios and it now skips the color ram test and all is working. If there is a color difference I canít see it. Happy days 🙂🙂

    https://ibb.co/GpbmMpz
    https://ibb.co/NSCYRKJ
    https://ibb.co/2qqMvL6

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