Sega CDX with messed pots

Discussion in 'Repair, Restoration, Conservation and Preservation' started by Romulo, May 16, 2018.

  1. Romulo

    Romulo Member

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    Hi there, how are you all?

    As the title says, I got a Sega CDX (In Brazil), from a person who did mess up with the pots (all of them), even after trying to replace the laser unit. So basically, it boots games (in cartridge) and it reads the first (and sometimes the second) track from audio discs (when I mess a bit more with the POTS).

    The seller in question messed with all the POTS and there is no way for me to know the original values. The other thing I noticed, is that when on battery, the console never turns on (I checked the voltage on the small PCB that connects to the bottom one and it seems fine).

    So, I googled around a bit, searched some forums and was able to find a user that had some POT values shown on the internet (If i remember well, he got them from a multimeter). Should I go and try to mess with them or it won't work that way? I know the Sega CD v2 manual states that you must calibrate the pots using a oscilloscope, but I'm wondering here if there is an easier solution.

    PS: If someone is able to mess/fix this in Brazil, talk to me!

    Thanks a lot :)
     
  2. Taijigamer2

    Taijigamer2 Peppy Member

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    Unfortunately it's not that easy. The pot values are different for every console. Using the sega cd model 2 as a reference, the correct way is with a calibration tool, test disc, oscilloscope, multimeter and frequency counter. The calibration tool and test disc are probably hard to come by but the other 3 tools can be acquired. You might be able to get away with a frequency counter, multimeter and a signal generator.

    Normally just the EF pot is adjusted when calibrating a new laser but the previous owner has blindly messed with all 3 pots. Using the sega cd model 2 service manual for reference, u will need to recalibrate all 3 test points.
     
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  3. Romulo

    Romulo Member

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    I see, thanks for the quick repply. So....that means that the readings I got for audio cd's now won't work for games right? At least in a stable way.
    Also, do you know anything about why the console wouldn't turn on from batteries?
     
  4. Droid III

    Droid III Rising Member

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    The test disc is a bog standard audio cd (unless my copy is a counterfeit).
     
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  5. Romulo

    Romulo Member

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    I can't even find any info on the CN403 adjustment jig they use :(
    Is anyone here capable of doing such measurements/corrections? Would be worth one's time?
     
  6. Bad_Ad84

    Bad_Ad84 The Tick

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    Apparently made to much tighter tolerances though. I have one too.
     
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  7. Romulo

    Romulo Member

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    News: I arrived at home, turned the sega cdx on again, it didn't read anything. Turned it off and when I tried to turn it on again, nothing No power. Nada. Tried several times, no luck. Measured the voltage on the power pcb and it was kinda low, measured the resistance on the capacitors (it is supposed to go higher and higher right?) and some of them are giving a quite low resistance, although I don't see any sight of leakage. I checked the voltage on the PSU (it's a very old original one) and its outputting 16V!!!! That's really high, no wonder why the batteries don't work anymore, I guess the PSU slowly fried the capacitors or the power board.
     
  8. Taijigamer2

    Taijigamer2 Peppy Member

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    The caps could need replacing on the power board. The only way to test properly is with a capacitor tester. The resistance test does not indicate 'health' of the cap. This video may be of some use with the pot values. Worth a shot. It may still need a new laser which might be why the previous owner was messing with the pots in the first place. Good luck.
     
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  9. Romulo

    Romulo Member

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    Nice, thanks for the video! I'll try to get my hands on a capacitor tester, and then see if the power board capacitors are faulty.
    I would also like to test the power supply capacitor, since it's outputting ~16V and these are bloody expensive. Too bad I'm still afraid
    to do it (so probably getting a technician to do it).
     
  10. Bearking

    Bearking Konsolkongen

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    Where can I get one, and would it work for all CD based systems?
     
  11. Bad_Ad84

    Bad_Ad84 The Tick

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    Think mine came from taobao? Don't really remember.

    Each console seems to have its own recommended test cd. I have a few others too.
     
  12. Droid III

    Droid III Rising Member

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    Such as? I'm genuinely curious. The one test CD I have even specifically states that all of its physical characteristics match the Red Book (aka the cd audio standard).

    As far as I know the purpose of these discs are to have patterns like left channel only, right channel only, 100hz sine wave, etc, all for testing purposes. And some generic music samples to check if everything sounds right..
     
  13. Bad_Ad84

    Bad_Ad84 The Tick

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    Basically, production discs can vary in quality. Test CD's are known to be of high quality.

    See picture of a book I have on testing/service CD players


    20180520_163516.jpg
     
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