Another Sega CD model 1 mystery.....

Discussion in 'Repair, Restoration, Conservation and Preservation' started by toto99303, Aug 9, 2016.

  1. toto99303

    toto99303 Member

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    Hi guys, I recently tried to resurrect a Sega CD 1 from the dead. Fuse has been replaced, caps replaced, SRAM chip for the game saves is replaced, battery replaced and optical lens replaced (Optima5, damn hard to find).
    Now console is powering fine, playing audio CDs perfectly, both burned CD-Rs and matrix. But not playing any Games, burned or original, no difference. It just stays on Bios screen with music and no text messages....
    Anyone had this issue? I even tried changing the BIOS with the same result.... It must be something in the main logic board....
     
  2. Poorcomputerman

    Poorcomputerman Active Member

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    I had mine recapped. This is the exact behavior after the recap. I tried the recapped board in two units and it does exactly what your unit does. The problem is definately on the board, but we can not figure out where.
     
  3. toto99303

    toto99303 Member

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    I'll try to trace most of the traces by schematic near all the caps I changed... I think it's a damaged trace somewhere...
     
  4. Poorcomputerman

    Poorcomputerman Active Member

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    I wish I knew what portion of the board was responsible for switching to game mode. The person working on my board checked the traces twice.
     
  5. Tokimemofan

    Tokimemofan Dauntless Member

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    Check the 315-5548, I have fixed several boards that had broken solder joints there.
     
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  6. Brad_83

    Brad_83 Blast Power Away!!!!

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    I've just recapped mine but i'm waiting for more parts to get it to a working stage. I"ll let you know if I have the same issues when It's up and running
     
  7. Poorcomputerman

    Poorcomputerman Active Member

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    The person fixing my board just resoldered all of the pins on that chip and the problem still exists. Any other ideas?
     
  8. Tokimemofan

    Tokimemofan Dauntless Member

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    Unfortunately not.
     
  9. Poorcomputerman

    Poorcomputerman Active Member

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    The interesting thing with my board was that everything worked fine before the recap. The capacitors were leaking, but the system worked.
     
  10. toto99303

    toto99303 Member

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    Same here, it was working before the recap....
     
  11. Poorcomputerman

    Poorcomputerman Active Member

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    I have seen a few posts over the years about audio cds working, but not games and I never saw the issue being solved.
     
  12. l_oliveira

    l_oliveira Officer at Arms

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    I had audio CDs working but game discs not working when my Japanese MEGA-CD had capacitor problems. I replaced all power related capacitors on the logic board (the SMD aluminum can capacitors), all power related capacitors on the analog/power board (of particular importance is the bigger one near the voltage regulator/heatsink) and all capacitors on the CD Drive board.

    My unit has the KSK-1200 SONY drive, not the JVC one.

    That solved the not playing game discs issue.
     
  13. Poorcomputerman

    Poorcomputerman Active Member

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    I tried a working drive board in the non-working drive board's unit and it worked. I have not replaced the power capicators yet. Could the difference in capacators be causing the problem?
     
  14. l_oliveira

    l_oliveira Officer at Arms

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    You replaced the laser? It could be misaligned.

    The rationale about the capacitors being a problem is that them not performing their function properly raise the noise level on the power rails, causing the drive to have "dirty" reads.


    That will cause a high error rate on the input of the CD-ROM decoder chip (the SANYO chip) and it will have too many read retries for data.
    Audio error correction is simpler and has a higher success data on recovering. Also, corrupted data from audio track on worst case scenario would mostly cause pops or skipping on the speaker.

    So, faulty capacitors end making the drive behave as if it was misaligned. Since you tested a known working drive and it works, it's time to put attention on the drive itself.
     
  15. Poorcomputerman

    Poorcomputerman Active Member

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    I actually ruled out the drive itself as both drives work with the processor board and memory board that was not recapped. The recapped one has only played audio since it was recapped. If I an understanding correctly, I should recap the power capacitors as that could cause the drive to not read correctly.
     
  16. l_oliveira

    l_oliveira Officer at Arms

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    If power is not stable, the drive will have difficulty reading discs. Audio discs are easier to read and will work even under low quality power.
     
  17. toto99303

    toto99303 Member

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    Anyone having other suggestions? I'm out of ideas...
     
  18. Arnold101

    Arnold101 Active Member

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    i have the same problem, the problem arrived just after putting in a bad working mega drive modded, after that i put again the original jap md unmodded and the mega cd now only read audio cd. 5 minutes earlier was reading games just fine. what i can check there?


    cpu board is recapped and power board i have recapped the 3x 100uf caps near the dissipator.
     
  19. Arnold101

    Arnold101 Active Member

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    also when i put the game i hear the lense making tic tic tic noise continuosly at the same speed the red access led is blinking, more fast than when no cd is inserted
     
  20. l_oliveira

    l_oliveira Officer at Arms

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    That means the pickup is not getting a strong enough laser signal back from the disc to attain proper focus on that specific disc. Might be that the lens are dirty (either the external lens or the pickup has dirt inside blocking the laser path) or the laser in the pickup is weak and is nearly dead. Sometimes bumping up the laser power adjust might help at getting some extra life out of the pickup (that's why the laser power pot exists to begin with).

    Fast blinking red led means it is trying to read something. If it fails, the unit will blink both leds and will open the tray, putting the disc out.
     

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