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Thread: Semi-working Genesis

  1. #16
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    You should have the components still, right? You removed them as the guide told you to. So just solder them back on and see if there is a difference in your video output.
    Anyway, the service manual for your genesis motherboard lists the EMI filter as STB101KB

    I don't want you to take it that I have the answer to your issue, I'm just saying that I found it unnecessary to remove the filter and the 75 ohm resistor to get better video with the cxa2075 install on Genesis model 3 and Sega Nomad.

  2. #17
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    Quote Originally Posted by rideordie71 View Post
    You should have the components still, right? You removed them as the guide told you to. So just solder them back on and see if there is a difference in your video output.
    Anyway, the service manual for your genesis motherboard lists the EMI filter as STB101KB

    I don't want you to take it that I have the answer to your issue, I'm just saying that I found it unnecessary to remove the filter and the 75 ohm resistor to get better video with the cxa2075 install on Genesis model 3 and Sega Nomad.
    Sadly, I damaged these parts and threw them away.
    I got 62 ohm resistors or I can get 75 ohm from 2x 150 ohm resistors. What to do with EM2 and that 240hm resistor connected to it, if I don't have EM2 atm? Will try changing just the resistors and post if there's any change.
    Sadly that filter with that number is nowhere to be found.
    Is there alternative I could use?
    Thank you!
    Last edited by Peeteris; 08-28-2019 at 08:57 AM.

  3. #18
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    I guess this could be the problem and the fix for it:
    https://bitsandblips.wordpress.com/2...video-encoder/

    I'll make an update when I'll receive necessary items and will try out the fix.

  4. #19
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    UPDATE:
    New 3.58MHZ Crystal on 6th leg of cxa2075 changed everything - picture is now without vertical lines or other artifacts.
    Why there's almost no info about this when most of the VA0 - VA1.8 model 2 Genesis systems are plagued with this?
    I hope this thread will help someone.
    If you have VA0 with Samsung video chip, just change it to any other or cxa2075, connect external crystal oscillator and, if necessary, add 2v to 14th pin of video encoder.
    Also, add Mega Amp mod and voilá, you got yourself a perfect Sega Genesis/MD console.

  5. #20
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    Awesome!
    I'm glad that you were able to tackle your issue.
    Sorry that my information and suggestions were not a fix. Hopefully, someone with the same problems can now refer to this thread for guidance, like you said.

    Is the new encoder a big improvement on video for this motherboard?

  6. #21
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    Quote Originally Posted by rideordie71 View Post
    Awesome!
    I'm glad that you were able to tackle your issue.
    Sorry that my information and suggestions were not a fix. Hopefully, someone with the same problems can now refer to this thread for guidance, like you said.

    Is the new encoder a big improvement on video for this motherboard?
    If color, shadows bleeding doesn't bother you (see the 1st post and images, that's still a problem) then absolutely. It had Samsung encoder with trash composite signal. Although if I would get such a console again, the first thing I would try would be to change 3.58MHz source. Maybe that would fix everything. I have done many things to this exact console that I can't revert it back to original state and try out other modifications.

  7. #22
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    Well, apparently not everything's so great.
    As it turns out, Composite video isn't working correctly. There's no colors.
    I guess it's something to do with the crystal, but not sure - what exactly.
    It's not that I use composite much, but it would be great to fix that.
    Any ideas?

    Thank you!

  8. #23
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    I investigated a bit and sadly my flair got it right.
    I knew that such an image console outputs if the oscillated signal is not correct.
    It turns out that my 3.58MHz oscillator actually outputs 3.14MHz.
    That's the best and the only type of oscillator I can get from a local store.
    How that even happened. Nevermind.
    Can I use resonators? They are cheaper and way more accessible. Or should I try to buy another oscillator?

  9. #24
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    Where are you located?
    I'm checking eBay and I see some.
    Digikey and Mouser have 3.58Mhz 5v cmos oscillators.

    Is PAL your native video signal?

  10. #25
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    You keep saying Genesis and not Mega Drive so I've been assuming that you have a NTSC console but you are asking about a 3.58Mhz clock signal which is PAL.

    When you did your cxa2075 encoder swap what value resistor did you use on pin 17 to 5v on the encoder?
    3.32k, 1% (NTSC) or 2.61k , 1% (PAL)?

  11. #26
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    Quote Originally Posted by rideordie71 View Post
    Where are you located?
    I'm checking eBay and I see some.
    Digikey and Mouser have 3.58Mhz 5v cmos oscillators.

    Is PAL your native video signal?
    I could buy an oscillator from Ebay, but I don't really want to wait for ~ a month to get the part.

    I'm from Latvia (Baltic States, Europe) and theoretically we have PAL, but I've got a NTSC Genesis system, so I used 3.32k, 1% on pin17->5V when I swapped encoders.

    I'm pretty sure that 3.579...MHz is for NTSC and 4.45MHz for PAL, therefore the problem is faulty oscillator itself.

  12. #27
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    I'm trying to help you the best that I can but I guess it is not much of a help. I am not knowledgeable on this video stuff, I do better at logic, I'm a PLC technician.
    Would this part from Mouser.com work for you? Does Mouser ship to you, and at a reasonable rate?
    https://www.mouser.com/ProductDetail...o5ehfmRGJaA%3D

    You are correct on NTSC frequency. I skimmed a crystal oscillator list, saw 3.575611MHz first for PAL and went with it.

  13. #28
    OPN2 in DNA Hedgehog-in-TrainingRoad Rasher Peeteris's Avatar
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    Thank you, will try to get a new oscillator and resonator, just for fun as I don't know how they work.
    That site offers FedEX shipping 20€. Ehrm, for 2€ component that shipping price is ridiculous, but expected.
    This is all that I can get from my local store: https://www.lemona.lv/?sn.q=3.579545
    Without pictures it's pretty hard for me to undertand if any of these are real quartz crystals.

  14. #29
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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  15. #30
    Hedgehog-in-Training Hedgehog-in-TrainingSports Talker rideordie71's Avatar
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    Peeteris,
    I have a spare, working model 2 genesis with a VA0 motherboard.
    You can have it for free but you would have to arrange and pay for the postage to your location.
    If you are interested, tell me, and we can start the shipping process and I'll get you a weight of the Genesis with packing.
    I am located in Cincinnati, Ohio, 45238, USA

    Also if you have a 32x I have confirmed on two of my model 2 VA0 genesis consoles that the 32x Sega Master System mod does work.
    ( http://www.sega-16.com/forum/showthr...-the-32X/page2 ) (post #24)

    You may want to try that mod out if you have the resources.
    Being able to play Master System games (with SMS adapter or using an Everdrive MD) without having to remove your 32x sure is a convenience.
    The mentioned mod also works on a VA1 Model 3 Genesis with the 32x compatibility fix. I have confirmed that to work on at least 2 of my own model 3's.
    Last edited by rideordie71; 09-22-2019 at 07:30 PM.

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