Results 1 to 10 of 10

Thread: Dead D4990?

  1. #1
    H = Hot
    M = Macho
    G = Gay
    HeavyMachineGun's Avatar
    Join Date
    Apr 2011
    Location
    Canada

    Posts
    3,810

    Dead D4990?

    I've got an MV-1T with a seemingly unfixable calendar error. Sometimes it shows a stuck green screen, other times it shows a black screen with "calendar error". I've already checked for +5v on the D4990 (which is present), replaced the oscillator a couple of times, reflowed the ceramic caps and even the D4990, but I still can't get to crosshatch or a game. The chip is kind of corroded, is it possible it needs to be replaced?

  2. #2

  3. #3
    Galford's Armourer

    Join Date
    Dec 2009
    Location
    Australia

    Posts
    452
    The calendar I/O goes through the NEO-F0 (see wiki pinout for specifics) so there may be an issue in that area too. Alternatively, you can try burning a diagnostic BIOS, hold ABCD on power on and go to calendar I/O test. It will show you the pin states in real time which may help us figure it out.

  4. #4
    H = Hot
    M = Macho
    G = Gay
    HeavyMachineGun's Avatar
    Join Date
    Apr 2011
    Location
    Canada

    Posts
    3,810
    Rise from your grave.

    Decided to take another crack at this MV-1T. This time I did some comparing against a good MV-1 (well, it has issues of its own, but it can boot to crosshatch).

    The only thing of significance I found was D4990 pin 4 was not connected to NEO-F0 pin 5, patched that. Still stuck on green. I then did some logic probing, nearly all pins seem good, except 12 and 13. Both were low, oscillator was new. I swapped 4 other 32.768Khz oscillators, they all are high on pin 12, low on pin 13.

    Are all my oscillators bad? Is my D4990 bad? It seems like only the oscillator is holding the board back from booting now.

  5. #5
    .
    Join Date
    Apr 2013
    Location
    Turkey

    Posts
    1
    Quote Originally Posted by HeavyMachineGun View Post
    Rise from your grave.
    Are all my oscillators bad? Is my D4990 bad? It seems like only the oscillator is holding the board back from booting now.
    no, you simply cannot get a reading directly at crystal legs (which are directly connected to 12-13 of D4990) with an ordinary logic probe. you "may" hear some signal for a very short time with "some" logic probes. only with an oscilloscope you can...

  6. #6

  7. #7
    Big Bang Pro Wrestler
    distropia's Avatar
    Join Date
    Apr 2010
    Location
    my workbench

    Posts
    1,040
    D4990 die easily. Try to swap.
    "appleTV-like" Consolized NeoGeo MVS builder (take a look here)

  8. #8
    H = Hot
    M = Macho
    G = Gay
    HeavyMachineGun's Avatar
    Join Date
    Apr 2011
    Location
    Canada

    Posts
    3,810
    Quote Originally Posted by yavuzg View Post
    no, you simply cannot get a reading directly at crystal legs (which are directly connected to 12-13 of D4990) with an ordinary logic probe. you "may" hear some signal for a very short time with "some" logic probes. only with an oscilloscope you can...
    I know, I was going by a repair log by channelmaniac. He checked a known working board and pins 12-13 showed high.

    Quote Originally Posted by Xian Xi View Post
    Did you burn a Diagnostic bios?
    If someone can tell me whether the Neo Geo BIOS (cart ROMs too) have to be byteswapped or not, I will burn one. I even made a thread, never got an answer.

    Quote Originally Posted by distropia View Post
    D4990 die easily. Try to swap.
    Ugh, really? Man that sucks, I already bought a new one for this board.

  9. #9

  10. #10
    Mr Neo Fix-it channelmaniac's Avatar
    Join Date
    Nov 2005
    Location
    Dallas, Texas Metromess

    Posts
    4,236
    I've rarely ever seen the D4990 bad... It's usually a bad crystal, dead traces, bad power trace, or a bad cap.
    Call me a cheap bastard... I learned to fix things to save money... even surface mount soldering...

    Visit my website: http://www.arcadecomponents.com

    ---------

    I've repaired boards for many members here.

    Want me to repair your arcade game board? Look here. I do MVS, AES, and many other game boards.

    My repair logs are have moved to NewLifeGames.com!!!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •