Weird Saturn issue

Discussion in 'Repair, Restoration, Conservation and Preservation' started by Pingu, Apr 28, 2019.

  1. Pingu

    Pingu Rising Member

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    So I recently put a VA 0 Saturn I've had in pieces back together again and I'm having a weird issue.
    Everything works perfectly with the top off. With it fully assembled though it doesn't validate game discs, it takes quite some time and then decides it's not a genuine disc. To make things even more weird the CD break even spins the disc backwards with the top on. The top case doesn't interfere with the disc in any way that I've found out.



    Does anyone have any idea of what could cause this?
     
  2. Bad_Ad84

    Bad_Ad84 The Tick

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    I've had this. Was a poor laser.

    Same thing, worked with top off and didnt with it on.

    Get another unit to swap over and test?
     
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  3. Pingu

    Pingu Rising Member

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    No compatible drive I'm afraid, guess I should bring out the oscilloscope and measure the RF level to start with then and maybe see if I can buy a new pickup somewhere.
     
  4. Oakleaf

    Oakleaf Spirited Member

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    The laser is probobly bad, but theres a chanse that the caps ar bad to. If you feel like it, change the caps to.
     
  5. Pingu

    Pingu Rising Member

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    You were right about it being a poor laser.
    So Apparently the laser is worn and using too much power dropping voltage. According to the Service manual voltage should be between .8 and 1.4V. I'm at around .7V I think.
    [​IMG]
    I guess I could give it a tiny bit more juice since it's borderline but yeah it's probably dying.
     
  6. Pingu

    Pingu Rising Member

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    Well it works as it should at 1.3V for how long I have no clue. The service manual does say that a new laser pickup should be installed since this one is dying so I'll do that if I can find one. You were spot on at least Bad_Ad84, thank you.
    [​IMG]
     
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  7. Oakleaf

    Oakleaf Spirited Member

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    just a tought (that i have also observed) when the caps are old and crappy, the laser RF pattern peak to peak might appear lower than with new caps.
     
  8. Pingu

    Pingu Rising Member

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    As in recapping the CD assembly or the whole system?
     
  9. Bad_Ad84

    Bad_Ad84 The Tick

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    In my instance, it wasnt caps.

    Machine also still works after tweaking the laser (and I did this at least 3 years ago)

    That said, I would certainly consider recapping the whole machine - saturns are starting to become a console that requires recapping in the last year or 2 (which at their age, is about right). If you have it open and intend to keep it - recap as preventative maintenance.
     
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  10. segasonicfan

    segasonicfan Robust Member

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    Pretty darn sure they mean the CD assembly. If it was the system power caps, you would get a voltage droop along all power rails.

    Very helpful pictures of the oscilloscope reading. Care to take a picture of your probes on the Saturn CD drive PCB? I'm sure it would help a lot of people down the road.
     
  11. Pingu

    Pingu Rising Member

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    If you mean the probe point I used here it is. Only valid for this drive model though I think?
    [​IMG]
    ground can be the shielding or any exposed metal part really.
    Keep in mind that when you use an oscilloscope that you need to isolate either the Saturn or the scope or you'll create a circuit through ground and potentially fry something along the way. So either put some Kapton tape on the ground prongs of the power cable going into the scope and measure with a multimeter that there is no connection to ground through the cable or pull the AV cord out of the Saturn so that you don't get a ground circuit through the TV.
     
  12. segasonicfan

    segasonicfan Robust Member

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    Awesome picture, thank you! I'm sure this will prove very helpful in the future.

    Good advice on the grounding. I imagine I can get away with using an AC inverter and a car battery too.

    For scope settings it looks like you're using 500mV divisions at .5u sec, yeah?

    And did you fix the laser p-p just by turning the orange potentiometer on the back of the circuit board? (By fix, I mean temporarily cuz I know these arent long-term repairs)
     
  13. Bad_Ad84

    Bad_Ad84 The Tick

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    You shouldn't need to make your scope float. This is also pretty dangerous.

    Your scopes ground clip is tied to earth. Connecting it to ground of the Saturn won't be a problem. Its only an issue if you are trying to connect your ground clip to other none ground points in the circuit. Also the Saturn uses a 2 prong power lead - it shouldn't be referenced to earth anyway.
     

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