Modding the Snes so the Tototek GBA-SNES adapter does not need separate AV cable.

Discussion in 'Modding and Hacking - Consoles and Electronics' started by MaxWar, Sep 15, 2013.

  1. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Ok so I built the circtuit on a protoboard and installed it in the SNES. It worked but I then discovered a small flaw in the circuit that I had not noticed before.

    When using the adapter with the mod you would get some interference in the form of light flickering slanting bars. It is quite subtle and mostly shows on blue/purple color but its one of those things that once you see you cannot unsee. This does not happen with the AD adapter connected directly.

    I traced the issue and it was caused by the fact that the MOSFET transistor does not seem to completely block the sync signal from the SNES even when its fully off with a solid 0v at the gate. There is always a trickle of signal going through that makes this interference.

    After trying various unsuccessful filtering methods I added another transistor and a ceramic cap to my circuit, to sink the sync signal when the system is in GBA mode.

    It works well but this is the very definition of a "dirty fix" lol. Goblin engineers would approve I am sure :p
    Still I am not fully happy with this, even though in practice it seems to work perfectly with no observable degradation of the signal in both modes.
    I am already thinking of the next version, the problem with this circuit is that it limits you to using composite

    [​IMG]
     
    Last edited: Oct 6, 2013
  2. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Here is a new circuit to use one cable with both Composite and S-video. Should allow to use the adapter in Composite along with Snes games in S-video.
    One drawback is that Snes games will no longer work in composite. But who cares when you have S-video?

    I decided to use a relay to switch chroma and luma, to maximise signal quality of S-video and prevent a potential Issue where a ghost signal leaked by a transistor could trip the receiving TV Composite/S-video switch.

    The main drawback of this is that it can only work on some TVs.
    *DO NOT USE THIS VERSION OF THE SCHEMATIC, YOUR SNES WILL CATCH FIRE!! ( Plz refer to next post for correct one :p )
    [​IMG]
     
    Last edited: Oct 11, 2013
  3. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    I have just finished my S-video Version of the mod.
    Here is a video Demo.



    Here is the Final form of the S-video version of the Mod:

    *This does not work on all tvs, on some tvs you will need to disconnect the S-video cable to get a composite image from the adapter.

    [​IMG]

    A picture of my install. Not the prettiest, cleanest job but everything is sturdy ( parts are held down with dabs of hot glue). The way I did the install, It all fits on the bottom of the SNES, motherboard but you need to get rid of the bottom RF shield.

    [​IMG]

    Thanks again to all who helped me getting this done! Special thanks to RetroSwim for teaching me about MOSFETS.
     
    Last edited by a moderator: May 25, 2015
  4. RetroSwim

    RetroSwim <B>Site Supporter 2013</B><BR><B>Site Supporter 20

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  5. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Thanks for the tip, will do!
    That might explain the "little problem" I had with my first take on the relay design.

    I was using a 12v coil relay and using the Unregulated current directly out of the power adapter.
    At some point when I was doing tests my Quad Gate IC started burning, it just fried and sent a puff of smoke.
    I found that the MOSFET transistor driving the relay had failed and shorted, which resulted in full unregulated 10ish volts to go to the gate input.
     
    Last edited: Oct 12, 2013
  6. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Just updated the schematic and picture, now include all the security fixes I was recommended.
    I hope this is the last version of this...

    Btw, the NEXT step in the evolution of this mod would be to try to revert the composite output of the adapter back into RGB and feed it to the Snes Encoder.
    Any one knows about ways to do this? That french RGB NES does it, maybe it could be used as a reference..
    But there are likely ready made IC solution to do this. Possibly chips that are inside TVs.
     
  7. armando92

    armando92 Member

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    if the chips outputs rgb before encoding it to composite for the av out then yes, but from you review of the cart i guess it doesnt.
    i suppose you will have to take a similar approach like they did with the N64 DAC, Tap in the digital signal and convert it to rgb. You can also use a chip from tv that takes composite and outputs rgb to the crt tube, my philips crt uses a TDA93XX/N3 (according to the oficial schematic), but i dont see the point in doing it this way since the source of the signal is still composite
     
  8. Pikkon

    Pikkon "Moving in Stereo"

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    The french NES outputs composite.
     
  9. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    The point is not to upgrade video quality, if anything It might downgrade it. The point is just to have the adapter work with any connection to the TV. Currently there is not point to this mod for people using RGB or Component modded SNES. Even my S-Video circuit above only works on some TVs.

    The best would be obviously to somehow get RGB out of the adapter but I doubt its possible, all there is on that thing is a big glob top chip. So reverting Composite back to RGB would allow much greater compatibility. And if the picture quality loss during the converssion is not significant then its worth it.
     
    Last edited: Oct 14, 2013
  10. armando92

    armando92 Member

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    well doesnt the rgb cable of the snes (SCART) can also work with composite video? i mean pin 20 says it is composite video / Csync in the pinout so changing a litle the wiring of the scart cable will be enough to use both rgb and composite with the same cable
     
  11. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Possibly but there might be issues If RGB uses composite instead of C-sync ( on the genesis it causes jailbars ) . I ordered a SNES scart cable last week to do some tests. There is likely a way to get this to work but it is once again a different mod circuit. And it would only work for RGB. Also I only have a PVM monitor which might behave differently then european TVs, so making something that works on my PVM does not garantee its compatibility on the Euro-scart standard.

    And It still does not solve the problem for those using component mod ( unless they use RGB-> component adapter )

    That is why I was interested in the Composite->RGB conversion. That would be the Universal mod that works on anything for everyone.
     
  12. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Ladies and gentlemen!

    I hereby announce you that at this point I have pretty much fixed all the most serious Sound issues that plagued the AD adapter.
    The only things that remains is it being mono, and also some occasional static, which is pretty minor.

    I fixed the weak audio problem on the SNES.
    I also Fixed the Terrible buzzing sound that afflicted the audio. It is now very clean.

    With those fixes considered, I officially consider this adapter SUPERIOR to the gamecube gameboy player ( For GBA that is, since it cant play regular GB )

    More details and tutorials for the fixes will follow later.
     
    Last edited: Oct 16, 2013
  13. RetroSwim

    RetroSwim <B>Site Supporter 2013</B><BR><B>Site Supporter 20

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    Going composite to RGB is non-trivial, you need to demodulate the colour part of the signal.

    I doubt there's an off-the-shelf part that does it, too. TV sets would do it internally, but it's likely to be integrated into an ASIC, not a dedicated part.

    Maybe have a look at some TV schematics?
     
  14. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    From my brief venture into taking apart CRTs and looking at chips inside, it seems that this function is done by chips that can be pretty standard in some cases. Like those used in mass produced no name brand tvs. The kind of chip you could get from UTsource.

    Anyway, not going to tackle this any time soon I think, unless someone comes over with a nice and easy solution. I would still be curious to take a peek in the French RGB NES though, to see how they did it.


    Right now i am neck deep into sound modding this adapter. I have made HUGE progress:
    The thing went from sounding weak and thin and noisy to pretty badass.

    -Stereo Sound works,
    -Noise issues are fixed
    -Working on optimizing volume balance and filtering levels.

    But I just lost a tiny SMD cap from the board while experimenting, Im pissed since I still kinda needed it... 1.3 uf...
    I am trying to find the best solution for sound while keeping it relatively simple. Losing this cap is a step back since I can no longer revert to stock. Good luck finding a new 1.3 uf ultra tiny SMD cap.
     
  15. marvelus10

    marvelus10 Spirited Member

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    Vacuum the room and then empty the vacuum into a bin and start digging. I have had to do this before, it worked.
     
  16. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Well, I said I lost it, but in truth I broke it xD
    I soldered a wire to one end and while moving it around the wire broke and took half the cap with it xD

    Bah, anyway the value was off so its not too bad. I was probably gonna junk it anyway.
    Stay tuned, epic audio mods for the AD adapter coming soon!
     
  17. drakon

    drakon Gutsy Member

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    This looks awesome. How much are these things?
     
  18. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    I got it about 40$ shipped from Tototek. But retro-bit more recently released one also, The "super retro Advance Adapter" around the same price. I believe It is the same thing with a different sticker but it might be an updated ( better ? ) version. I would be curious to see inside.
     
    Last edited: Oct 19, 2013
  19. Helder

    Helder Site Supporter 2014,2015

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    Last edited: Oct 19, 2013
  20. MaxWar

    MaxWar <B>Site Supporter 2013</B>

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    Last edited: Oct 19, 2013

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