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Thread: Sega CD systems repair thread

  1. #661
    Hedgehog-in-Training Hedgehog-in-Training jrdoran's Avatar
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    Quote Originally Posted by ironnick23 View Post
    In the back left corner of the cd tray is a plastic tab on the lid that pushes a sensitive switch on the inside which indicates open/close. This is either out of alignement or the switch itself is broken. Try opening the shell and with you fingers pinching this switch to imitate the cd lid being closed. If you cannot it sounds like this component needs replacing. Be mindful when putting the shell back on that you keep the cd tray open as to not damage this switch when reassembling. As a last resort there may be a way to solder a wire on the underside of this switch that will always make the system think the lid is closed on boot, though this is not ideal.
    Hi thanks for the reply! The plastic tab on the underside of the lid looks to be intact regardless I've booted it up with the lid off and pinching the door switch to ensure its being activated. No luck though as it will still boots to "close cd door". I think the door switch is functional because I used a multi-meter and was able to get a response when pressing the switch together and testing on the solder points. Is there another way to verify the door switch is operational?

    If I needed to bypass the switch do you know at which points on the board I would need to solder the wire?

  2. #662
    Hedgehog-in-Training Hedgehog-in-TrainingNameless One pyroesp's Avatar
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    Quote Originally Posted by jrdoran View Post
    Hi thanks for the reply! The plastic tab on the underside of the lid looks to be intact regardless I've booted it up with the lid off and pinching the door switch to ensure its being activated. No luck though as it will still boots to "close cd door". I think the door switch is functional because I used a multi-meter and was able to get a response when pressing the switch together and testing on the solder points. Is there another way to verify the door switch is operational?

    If I needed to bypass the switch do you know at which points on the board I would need to solder the wire?
    How did you check the switch ? Just measuring voltage or using the continuity mode of the multimeter ?
    I'd test the switch in continuity mode, measuring on the PCB solder points of the switch.

    If that's ok then you probably have a broken trace.
    Last edited by pyroesp; 09-02-2018 at 07:32 AM.

  3. #663

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    Hi all. So fixing up a dead Mega CD is my current project (hoping to have it ready in time for the Mega Sg arrival!).

    Setup - PAL Mega Drive 1 - PAL Mega CD 2

    Mega CD 2 is generally in good clean condition internally and I've given the slot a good clean with IPA.

    Current symptoms - Mega CD does not power up - no LED no disc spin

    So I've done the initial tests.

    PSU is fine
    Fuse is fine
    V Reg is spitting out 5v on pin 3 as expected

    When I power cycle the Mega Drive my TV does detect a signal (576p) and I see some slight ripples in an otherwise totally black screen.

    Just wondering what my next steps should be?

  4. #664
    Hedgehog-in-Training Hedgehog-in-TrainingNameless One pyroesp's Avatar
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    Check if voltage is present on all the ICs.
    Even without CD you should see the mega cd boot up screen.
    The LED is controlled by an output of IC101, and I think only lights up when reading a disk.
    You can check the oscillator to see if that's still working.

    Are the capacitors ok ? No leakage ?

  5. #665

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    Quote Originally Posted by pyroesp View Post
    Check if voltage is present on all the ICs.
    Even without CD you should see the mega cd boot up screen.
    The LED is controlled by an output of IC101, and I think only lights up when reading a disk.
    You can check the oscillator to see if that's still working.

    Are the capacitors ok ? No leakage ?
    Caps all look fine visually. I'll get a meter on the ic vcc pins and see what we've got.

  6. #666
    Hedgehog-in-Training Hedgehog-in-Training Amerika's Avatar
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    Sound distortion/echo issue with a Sega CD Model 2

    I captured some footage of the issue so please give it a listen. It's bizarre.



    https://www.youtube.com/watch?v=y16YV9jljPo



    I'll copy/paste what I put into the videos description to give you guys an idea of what this thing is and what has been done.



    This is a model 2 Sega CD that I picked up which was sold for parts/broken. Somebody had done a really bad repair job on it and the Q301 transistor and the fuse was blown out. I also removed the new caps they put in and replaced all caps with my own. That fixed the unit and CD's read just fine (even Sylpheed) but I get the sound issue you hear in the video. This is a Funai motherboard (the version with the out of place daughterboard) and it also has the SOHOT4 Samsung laser in it rather than the Sony KSS-210A. And I did replace c412 with an 47uF 6.3v capacitor. Maybe that capacitor isn't doing what it should be? I've also cleaned up and re-greased everything that could use it and I also adjusted the pots (had to do it blind since I don't own a scope..but I took photos of stock positions) and no change. I guess one of the new caps I used could be bad. I did reflow all of them just to be sure.

    Any other ideas?

  7. #667

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    I have an X'Eye that I've had in my to-fix pile for years. I think it might have been someone else's parts machine.

    Video of symptoms:
    https://www.youtube.com/watch?v=P9Xv-FymyKM

    If you watch closely, it doesn't crash the same way every time. The Sega logo seems to be getting drawn in a few different ways (cartridge is Columns), almost like some other part of the game logic is waiting on a timer task to complete (DMA? Collision detection? Wild guess...) but is never getting quite there.

    Text and graphics are corrupted in the CD BIOS (it will tile, drop layers, or glitch) and eventually it freezes solid. Music playback sounds great and is 100% perfect - on the RCA AV cables. It will continue long past the freeze, and doesn't seem to get stuck in a stutter-loop - playback is perfect.

    On the RCA jacks, game cartridges never get to TMSS - just a black screen, no sound.

    On the Genesis AV cable, I don't get any music playback in the CD BIOS, but the video is the same.

    Trying to load from a cartridge on a Genesis AV cable (in the video), I get all kinds of weird behaviour, but can generally hit reset and try again. I am repeatedly hitting reset in the video. I'd say TMSS succeeds every single time the machine is cold started, unless the cartridge is bumped in the slot.

    No matter what is running, the JVC will eventually freeze, and if I wait long enough after it freezes, even reset will stop working. It doesn't run long enough in the CD BIOS to be able to start an audio CD or Sega CD.

    I eyeballed the caps and traces - caps don't look bulged or leaky, traces look fine. I plan to take a closer look at the legs of the ICs tomorrow with a webcam microscope.

    I don't have an ESR tester so I'll have to source one in order to test the caps that Jeroi mentioned in this post. I'm hesitant to go shotgunning capacitors into this thing without understanding what's going on.

    I still can't load carts with the CDROM board disconnected, and the BIOS will still glitch/freeze with no cartridge installed.

    With the CDROM board connected, I sometimes hear a click on cold start that is probably engaging the disc drive motor.

    With the top removed, the CD BIOS can detect that the lid is missing and complains to insert a disc. It didn't seem to lock up during this test, but the graphics were still corrupted.
    Last edited by seat safety switch; 01-02-2019 at 10:56 AM.

  8. #668

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    I found a little bit of corrosion on (at least) pins #192 and #193 on the VDP, which the console5 wiki says is "UDS and LDS 68000 interface." I'm guessing that's related to DMA.

    I tried cleaning them a bit with alcohol and a q-tip but the corrosion is pretty nasty and doesn't want to budge.

    My current theory is that the corrosion goo is bridging the pins just enough that DMA block transfers get corrupt, and then eventually someone notices and pulls the handbrake on the 68K (bringing the halt pin low).

    I am guessing the red and white grease pencil on the VDP means someone else noticed this before me.

    Some pictures (apologies for the crappiness of my desktop USB microscope, its stand is useless).




    Aerial view of the area:


    X'Eye bios pictures:



    I still get music in the X'Eye BIOS, so I'm guessing however they wrote the BIOS doesn't use DMA to program the YM. Sometimes I get sound effects or a stuttering first note from Columns.

    Update: The UDS, LDS pins, despite looking really gross, have continuity with the ones on the 68K, but the /DTACK pin is not, despite its apparent mint condition.

    I'm unsure why that would be (the trace on the board is not very long and does not appear to have any useful test points - maybe the pad is bad?). Waiting on a better microscope stand so I can try to see it well enough to solder a patch wire between the 68K and the /DTACK pin on the VDP.

    Deoxit cleaned up some of the corrosion but not all.

    Update 2: With some better lighting and magnification (until the new microscope stand snapped), I traced DTACK all over both sides of the board to find a surface-mount resistor in the way, which is why DTACK initially didn't seem to have continuity. Seems fine now.

    There are some stick-on glue pads on the underside of the board to hold some very poorly soldered and flux-soaked factory patch wires in place. I've seen those pads turn acidic/trap cap goo in PC98s and there was one quite close to the VDP, so I removed the one directly under C252 (seems to be related to the ground plane of the VDP). Under the pad, I found that all the solder around the positive leg had corroded - the leg was loose in the via on the underside! - and that the cap had leaked. Resoldering the leg didn't do anything except sizzle and smell like burning cap goo.

    Waiting on an order of some replacement caps.

    Update 3: I replaced C252 (the cap with an ugly leg, under the glue pad) and C206 (its buddy next to it, close to the VDP pins that were corroded). No effect. I've noticed that the TMSS screen is always perfect. Wonder how that mechanism differs from when it's drawing otherwise. Maybe it is RAM? My Everdrive won't load far enough to try a RAM test; it locks up on a solid green screen after TMSS.
    Attached Images Attached Images
    Last edited by seat safety switch; 01-25-2019 at 12:34 AM.

  9. #669
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    and if the cd1 read any cd audio i put in but no games? even if 5minutes before the problem readed games perfectly. now it doný't read games anymore, only audio


    please help me

  10. #670
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    i hear that the lens is making a continuous very gentle tic tic tic noise, and it goes at the same speed of the access red led. maybe is really the lens the problem?

  11. #671
    Video Game Modder Outrunner segasonicfan's Avatar
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    Quote Originally Posted by seat safety switch View Post
    I have an X'Eye that I've had in my to-fix pile for years. I think it might have been someone else's parts machine.

    Video of symptoms:
    https://www.youtube.com/watch?v=P9Xv-FymyKM

    If you watch closely, it doesn't crash the same way every time. The Sega logo seems to be getting drawn in a few different ways (cartridge is Columns), almost like some other part of the game logic is waiting on a timer task to complete (DMA? Collision detection? Wild guess...) but is never getting quite there.

    Text and graphics are corrupted in the CD BIOS (it will tile, drop layers, or glitch) and eventually it freezes solid. Music playback sounds great and is 100% perfect - on the RCA AV cables. It will continue long past the freeze, and doesn't seem to get stuck in a stutter-loop - playback is perfect.

    On the RCA jacks, game cartridges never get to TMSS - just a black screen, no sound.

    On the Genesis AV cable, I don't get any music playback in the CD BIOS, but the video is the same.

    Trying to load from a cartridge on a Genesis AV cable (in the video), I get all kinds of weird behaviour, but can generally hit reset and try again. I am repeatedly hitting reset in the video. I'd say TMSS succeeds every single time the machine is cold started, unless the cartridge is bumped in the slot.

    No matter what is running, the JVC will eventually freeze, and if I wait long enough after it freezes, even reset will stop working. It doesn't run long enough in the CD BIOS to be able to start an audio CD or Sega CD.

    I eyeballed the caps and traces - caps don't look bulged or leaky, traces look fine. I plan to take a closer look at the legs of the ICs tomorrow with a webcam microscope.

    I don't have an ESR tester so I'll have to source one in order to test the caps that Jeroi mentioned in this post. I'm hesitant to go shotgunning capacitors into this thing without understanding what's going on.

    I still can't load carts with the CDROM board disconnected, and the BIOS will still glitch/freeze with no cartridge installed.

    With the CDROM board connected, I sometimes hear a click on cold start that is probably engaging the disc drive motor.

    With the top removed, the CD BIOS can detect that the lid is missing and complains to insert a disc. It didn't seem to lock up during this test, but the graphics were still corrupted.
    I recently repaired a CDX with similar symptoms. It looks like a VRAM issue. If you get to TMSS then your 68K and connections are likely fine. I vote that its your MSM54C864-10 (IC192) and / or shorted connection issues to it with the 315-5660. My CDX would load the sega logo and glitch out similarly. It was that chip, and a short to GND on the VRAM bus (a dead 315-5660 pin yuck).


    Arnold101, sounds like it's time for a new laser.

    -Segasonicfan

  12. #672
    Video Game Modder Outrunner segasonicfan's Avatar
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    I made a bunch of Sega CD model 1 repair videos to share for free. These go over some of the nitty-gritty headaches that are not well documented for tray issues with the model 1. I watched quite a few videos on YouTube and couldn't find the necessary information, so here ya go:

    https://www.youtube.com/watch?v=jtXI...3IVIfeBQ9Lax7u

    Note, since I make all my videos for free (they are quite time-consuming) you will have shaky camera, no editing, etc. There are much better production-value videos on youtube with much worse technical information. I just try to focus on what's important (the knowledge, yeah!)

    -Segasonicfan

  13. #673
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    new laser my a$$. I fixed it

  14. #674
    Hedgehog-in-Training Hedgehog-in-Training Bizous's Avatar
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    Hello everyone
    I buy a Sega Mega CD1 Jap down.
    When I turn it on it show me glitch.
    http://mickael.games.free.fr/PHOTO/MEGACD1VIDEO.avi
    So I dismount the mega CD.
    And I find this pieces in the bottom of the console.

    What is this pieces ( ALPS472 ) ?
    I found this on the maintenance service ==>( 477-0005 : R-PACK 8*4.7KOHM 1/8W W/COMMON )
    I can not find the same thing or equivalent of this piece to put a new one.
    Can you help me
    thank you in advance

  15. #675
    Video Game Modder Outrunner segasonicfan's Avatar
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    Quote Originally Posted by Bizous View Post
    Hello everyone
    I buy a Sega Mega CD1 Jap down.
    When I turn it on it show me glitch.
    http://mickael.games.free.fr/PHOTO/MEGACD1VIDEO.avi
    So I dismount the mega CD.
    And I find this pieces in the bottom of the console.

    What is this pieces ( ALPS472 ) ?
    I found this on the maintenance service ==>( 477-0005 : R-PACK 8*4.7KOHM 1/8W W/COMMON )
    I can not find the same thing or equivalent of this piece to put a new one.
    Can you help me
    thank you in advance
    Yikes, you're going to need to do a full recap and other work in addition to that part. That is simply a resistor array, very easy to replace. Its just 4x 4K7 resistors.

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