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Thread: Sega Mega CD repair

  1. #1
    Old Man
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    Question Sega Mega CD repair

    So, recently bought a Mega CD, knowing that it may not be working properly.

    Sure enough, I got it home and it was dead.

    Recapped the power board and tried again.

    Success - unit came on, and the splash screen came up but the sound was garbled.

    Switched it off, cleaned all the contacts, tightened the slots the mobo and Mega Drive connect to and tried again.

    Some improvement but not significant.

    So I decide to recap the mobo as that seems to be a given thing to do with most of these old MCD units.

    Put everything back together and now all I can get is this:



    And there's like a muffled clicking / popping noise coming out of the speakers.

    What am I missing here?
    Bonuskun - "Please young man. You telling me to shut up on an internet forum is about going to have the same effect of trying to tell Tarma that Metal Slug 4 was the best Neo Game ever.

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  2. #2
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    Double-check the ribbon cable between the CD drive and the CPU board. Usually if only the background is displayed it means that the CPU board can't communicate with the CD drive.

    I see that you recapped the power board and CPU board already. You should recap the CD controller board and laser unit while you're at it. They're through-hole caps, so they're pretty easy to deal with.

    Had any of the SMD caps leaked on the CPU board? If so, there may be damage to one of the traces nearby. Clean throughly and check any suspicious traces with a continuity tester.

    Here's a sample from a Model 1 Sega CD I'm repairing right now - note that the trace to the right of the Sanyo chip was eaten away by leaked electrolytic from the nearby cap:

    IMG_2414.jpg

  3. #3
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    If your Mega CD has a socketed EPROM for the BIOS, carefully pry the EPROM out and check the pins on the socket as well. On this other Sega CD I repaired, leaked electrolytic from the nearby cap ate away one leg of the socket and caused problems.

    IMG_2444.jpg
    Last edited by ShootTheCore; 07-25-2019 at 05:48 PM.

  4. #4
    Old Man
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    Ah, well I think the ribbon cable between the CD-drive and the mobo is fucked - do you know where I could pick up a replacement? I've tried searching online and found similar ribbons, but nothing that I'm convinced is identical or a suitable alternative.

    I'll double check the mobo but I'm sure all the tracks are ok and there's been no real leakage issues.

    Yes, got the socketed BIOS, everything looks ok, but I've not removed the chip... last time I removed a socketed chip I snapped a foot!!
    Bonuskun - "Please young man. You telling me to shut up on an internet forum is about going to have the same effect of trying to tell Tarma that Metal Slug 4 was the best Neo Game ever.

    Not going to happen."


    Argentina'94 - "Gotta admit, that was the best coffee and cigarette I ever enjoyed with someone who wasn't in front of me. We MUST do this again!"


    Peanutbutterjammatime

  5. #5
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    Pretty sure this will work for replacing the ribbon cable:

    https://www.ebay.com/itm/FFC-A-25Pin...cAAOSwLnBX975U

  6. #6
    Old Man
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    Awesome! Thanks for the link - I've ordered one, and we'll see what happens when it gets here.

    In the meantime I'll check those other bits when I'm back from work tomorrow.

    Do you know what might be causing the sound problem?
    Bonuskun - "Please young man. You telling me to shut up on an internet forum is about going to have the same effect of trying to tell Tarma that Metal Slug 4 was the best Neo Game ever.

    Not going to happen."


    Argentina'94 - "Gotta admit, that was the best coffee and cigarette I ever enjoyed with someone who wasn't in front of me. We MUST do this again!"


    Peanutbutterjammatime

  7. #7
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    Is the Mega CD BIOS music playing with the clicking sound over the top of it? Or is it quiet except for the clicking?

    If it's quiet except for the clicking, I expect the BIOS is in a loop restarting the sound system over and over while it attempts to detect the CDROM drive. If that's the case, the clicking should go away once you get the new ribbon cable in place and the drive is detected.

  8. #8
    Old Man
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    Quote Originally Posted by ShootTheCore View Post
    Is the Mega CD BIOS music playing with the clicking sound over the top of it? Or is it quiet except for the clicking?

    If it's quiet except for the clicking, I expect the BIOS is in a loop restarting the sound system over and over while it attempts to detect the CDROM drive. If that's the case, the clicking should go away once you get the new ribbon cable in place and the drive is detected.
    There's no noise other than the clicking... the boot menu tune is not playing at all at the moment.

    I'll post another update as soon as the ribbon arrives... not much to add until then... other than I really appreciate the advice and help
    Bonuskun - "Please young man. You telling me to shut up on an internet forum is about going to have the same effect of trying to tell Tarma that Metal Slug 4 was the best Neo Game ever.

    Not going to happen."


    Argentina'94 - "Gotta admit, that was the best coffee and cigarette I ever enjoyed with someone who wasn't in front of me. We MUST do this again!"


    Peanutbutterjammatime

  9. #9
    Old Man
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    So, ribbon cable arrived... not identical to the one out the unit. Same pins, but slightly slimmer and not as thick - not sure if it's suitable for CD to mobo connectivity - tried it, but same issues as previously. Swapped the ribbon on the power board and that works fine, so not a completely wasted purchase.

    Still, unit still won't anything other than a static screen and no sound.

    Is a chip fucked perhaps? How would I test them?

    Me thinks I need to buy another unit and chop and change parts.
    Bonuskun - "Please young man. You telling me to shut up on an internet forum is about going to have the same effect of trying to tell Tarma that Metal Slug 4 was the best Neo Game ever.

    Not going to happen."


    Argentina'94 - "Gotta admit, that was the best coffee and cigarette I ever enjoyed with someone who wasn't in front of me. We MUST do this again!"


    Peanutbutterjammatime

  10. #10
    Big Bang Pro Wrestler
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    Quote Originally Posted by Tarma View Post
    So, ribbon cable arrived... not identical to the one out the unit. Same pins, but slightly slimmer and not as thick - not sure if it's suitable for CD to mobo connectivity - tried it, but same issues as previously. Swapped the ribbon on the power board and that works fine, so not a completely wasted purchase.

    Still, unit still won't anything other than a static screen and no sound.

    Is a chip fucked perhaps? How would I test them?

    Me thinks I need to buy another unit and chop and change parts.
    I'm still pretty sure your problem is with either the CD-ROM board or the connection to it. Here's what I suggest:

    1) With the ribbon between the CPU board and CD-ROM board connected, test continuity between each pin with each board that the ribbon connects. Every pin should be connected.

    2) Replace all the capacitors on the CD-ROM board. There's a lot of analog signals involved with controlling the CD-ROM and dried or failed capacitors will cause fluctuations with those signals.

    3) Finally, try purchasing another console and try trading the CD-ROM.

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