Replacing the DC PSU

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

  1. Korn16ftl3

    Korn16ftl3 Robust Member

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    I was speaking in terms of a saturn mod for the rtc, this psu replacement is also very common for a saturn as well
     
  2. Nopileus

    Nopileus Rapidly Rising Member

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    Nope, still all glitchy and weird with it removed.
    Only way to clear the weird shit was switching the 12v input on my system.
     
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  3. Xerxes3rd

    Xerxes3rd Rapidly Rising Member

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    That's really strange; maybe the PS_ON pin needs to have a pullup on it (since it's supposed to be active low)? Floating should be fine, but maybe it's not.
     
  4. Korn16ftl3

    Korn16ftl3 Robust Member

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    Wonder what would happen if we add'd a load to ground and ps_on.....from the old guides for making a bench top psu from an older pay the older psu's needed a load on the ps_ok wire between it and the ground.... just a thought?
     
  5. Xerxes3rd

    Xerxes3rd Rapidly Rising Member

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    I thought most of those load requirements were from ATX PSUs, which won't function properly if there's no load on the 5V and/or 12V lines. If the PicoPSU required a load on for the PS_OK wire, then why would it be working OK without the Dreamcast's switch connected (not trying to be argumentative here, just wondering)? Also, the PS_ON pin should just be a logic high/low, and I wouldn't think would require much current. I suspect the best thing to do would be to put a scope on it with and without the Dreamcast's switch in-line and see what's going on.
     
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  6. Korn16ftl3

    Korn16ftl3 Robust Member

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    I was just throwing out a possibility I'm curious as to why you can use the saturn switch connecting ground to ps_on on a saturn but not on a dreamcast, it just seems odd to me. Either way I'm preparing to swap my saturn psu out with a pico for the sole purpose of stepping down the 5v standby to 3v and eliminating that stupid battery issue once and for all....at least for the duration it's plugged in for.
     
    Last edited: Nov 29, 2017
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  7. Mikey242

    Mikey242 Member

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    Hey guys, I finally bit the bullet and had a go at this mod for the Dreamcast. At first it was all working well, but I would sometimes get random reboots. Now the Dreamcast won't properly switch on. When I press the power button the fan starts turning and the Dreamcast led flashes on then off again immediately.

    To power the system on I have the PS_ON soldered to GROUND and have the DC's power switch connected to the 12V input cable to the PSU.
    On the rails I am measuring 0.91v from the 3.3v, 5v from the 5v and the 12v rail slowly drops when measuring it.
    I am using a non-branded PicoPSU and a GDemu.

    Is this a problem caused by using a cheaper PSU? Any advice greatly appreciated.

    EDIT: Clarification
     
    Last edited: Jan 30, 2018
  8. Collingall

    Collingall Robust Member

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    What is your external power brick rated for?
     
  9. Mikey242

    Mikey242 Member

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    It's 12V 5A
     
  10. AndehX

    AndehX You got boost power!

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    I could simply be a faulty PicoPSU. I'd try a different one.
     
  11. Mikey242

    Mikey242 Member

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    Yeah I'm starting to think so too. I've ordered a mini-box one this time and will report back if it solves the issue. That's what happens when you order a cheaper one I guess.
     
  12. AndehX

    AndehX You got boost power!

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    Yeah it can happen. I bought a cheap one for mine too, but mines working fine. Luck of the draw I guess.
     
  13. Mikey242

    Mikey242 Member

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    Yeah I'm sure I was just unlucky.

    Got my mini-box psu yesterday and it seems to all be working fine now. Before installing the new one I tested my old one again and it didn't immediately work, but after about 5 seconds of being powered on, the light suddenly came on and it booted up. I guess the 3.3v rail was just a bit dodgy on mine.
     
  14. earthshaker

    earthshaker Member

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    Just a probably stupid question.. if I buy a 160W picoPSU, shall I use a 160W brick DC? or can I use a 60? I mean, shall the power supply watt match the same Picopsu value?
    Thank you!
     
  15. Collingall

    Collingall Robust Member

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    You will be fine with a lower powered brick. I use a 60w supply on my 80w PicoPSU
     
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  16. earthshaker

    earthshaker Member

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    Perfect, Thank you!
     
  17. earthshaker

    earthshaker Member

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    Hi guys, I just mounted the PSU, but I have some video interference when I use my internal VGA. When I use the normal RGB everything works fine. I tried to desolder the 12v cable to see if something changes but the interferences remain. Any good advice? here is my PSU and my brick (bought from Amazon).
    [​IMG]
     
    Last edited: Jun 2, 2018
  18. SONIC3D

    SONIC3D Spirited Member

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    I'm not professional in electronic. But if I met such situation, I would:
    1. Try switch back to your original PSU board to see if you have VGA signal interference. To make sure it's not caused by VGA cable/box(especially if it comes from 3rd party production).

    2. Try to make the board a bit far away from the console to see if it's still interferenced.

    Hope it would be helpful.
     
  19. -=FamilyGuy=-

    -=FamilyGuy=- Site Supporter 2049

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    The 12V wall PSU might be noisy, try another one to see if it changes interference.
     
  20. earthshaker

    earthshaker Member

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    With the original board I don't have any interfaces and even if I move the board I still have it.


    Do you recommend me to test and buy another PSU?
     

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