Replacing the DC PSU

Discussion in 'Sega Dreamcast Development and Research' started by Rocky5, Sep 26, 2014.

  1. Nully

    Nully Intrepid Member

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    I'm not sure what's wrong with my chinese clone aside from the fact it's a chinese clone. I tried jumping it and starting a few devices and booting a mini-itx motherboard, but it won't do anything at all and there's no LED indicators. I'm getting 12v output on the board and have used several amperage rating 12v power supplies. Seller won't cover return shipping back to Hong Kong or refund. Am I missing any extra steps to get some basic verification that it works before doing the mod, there isn't any documentation with troubleshooting these clones.
     
  2. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    I'd try to find another 12 source first, maybe an ATX PSU or some other 12V wall adapter.

    If the 12V psu is noisy, your VGA wires could pick up the signal like little antennas, resulting in visible interference. You could also try to filter the 12V by putting a capacitor between 12V and ground as early as possible in the circuit. And you could twist the 12V and GND wire of the PSU together.
     
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  3. earthshaker

    earthshaker Member

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    I see, I will follow your advice, let' s see what happen. However yesterday I tried to desolder the 12v wire, but the intereference remained.
    Do you also recommend to remove the blue MOV by the power switch?
    Thank you for your precious advices!
     
  4. truemaster1

    truemaster1 Gutsy Member

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    remove or not remove the mov will not change anything. avoid power supplies from china they are bad, and are responsible for the noise
     
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  5. earthshaker

    earthshaker Member

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    I see, I bought it coz many Amazon users left a positive feedback for that. Then I will buy another one. Unfortunately are all made in china, and I dunno which one to buy. What about this, it has almost 400 positive feedback (sorry it is in italian language)?
    https://www.amazon.it/Salcar-alimen...TF8&qid=1528014261&sr=8-7&keywords=psu+12v+5A
     
  6. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    It's actually hard to tell unless you try. The problem is that a noisy PSU works well enough for most applications; you just happen to have an unshielded VGA signal in the console that can pick up the noise. IIRC, a Gamecube PSU is pretty good, so you might try that if you have one at hand.
    You need to connect a certain pin to ground in order to simulate the power button of the PC being pressed on. IIRC it's pwr_on or similar, look around in the thread and it'll be detailed, or look into my 11 years old threads on dcemu... I think I'm getting old...
     
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  7. earthshaker

    earthshaker Member

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    First of all thank you for your precious advices. Don't you recommend me to buy and try a different brik power supply then? I should have a Gamecube PSU somewhere, I will try to test it. My VGA mod is the mmmonkey one, same wiring and components. If I shield it, may I fix the problem then? How can I shield it?
    Honestly, as I reported on another thread, that VGA mod gives me some scanlines (vertical lines) on my LCD (even with the original board), but I thought it was my tv as I tested also a VGA box a couple of days ago and it gives me the same problem.
     
    Last edited: Jun 3, 2018
  8. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    A better PSU could fix your problem, but it's not guaranteed. If you can spare the change, go for it, but don't buy the cheapest Chinese one you can find.

    Ideally, you would have access to a stable 12V source to test beforehand if the PSU really is the culprit.
     
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  9. earthshaker

    earthshaker Member

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    As you recommended me I tried the gamecube one, and everything works perfectly! Then the problem is the PSU! I have two possibilities: buy another original gamecube one and modify the output jack or buy a universal one more expensive. However thank you for your advice, really made my day!
     
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  10. Crystal Shyps

    Crystal Shyps Member

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    This is pretty slick looking: https://github.com/chriz2600/PicoDreamcast.

    Looks like for all parts (minus the PicoPSU and DC power supply) comes out to ~$20 before shipping costs... but that's with a 5-pack of the connectors from Ali Express, and the OSH Park seems to say that it's the cost for 3 PCBs (is that just how it counts each board?), so it might be way cheaper that that per unit if buying in larger quantities. Looks like if you buy 15 it would be like $6.50 each, assuming that $13.30 price on OSH Park really is for 3 boards.
     
  11. Collingall

    Collingall Robust Member

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    Order from https://jlcpcb.com/ you will be in for $10 shipped for 10 pcbs
     
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