N64 RGB Mod - Poor quality image

Discussion in 'Modding and Hacking - Consoles and Electronics' started by fathertime, Jul 16, 2011.

  1. link83

    link83 Enthusiastic Member

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    No because not all N64's use the VDC-NUS chip - unless you mean all N64's that are easily RGB moddable, in which case yes C-Sync output is available on the VDC-NUS chip, but its unbuffered and not connected to the MULTI OUT port on some revisions.
     
    Last edited: Jul 24, 2011
  2. Bad_Ad84

    Bad_Ad84 The Tick

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    Yes, by "RGB moddable" I did mean "Easily RGB moddable without replacing the DAC with a DIY one". I should probably have been more specific.

    Which I assume the OP has bought too, rather than the DAC method.

    Also, please see my edit on the previous post. Thanks again for the input.

    edit:
    The guide I used on GameSX did already mention about C-Sync, but is wrong according to your above posts.

    http://gamesx.com/wiki/doku.php?id=av:snes2rgb
     
    Last edited: Jul 24, 2011
  3. link83

    link83 Enthusiastic Member

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    No offense intended (Hope I dont come across as a know-it-all), I just find that statements online need to be clear, otherwise people misinterpret what was written (eg. "I read online that all N64s have C-Sync output, but my mod doesnt work!" - I get PM's like this quite often!)

    <EDIT> Glad I could help :thumbsup:
     
    Last edited: Jul 24, 2011
  4. Bad_Ad84

    Bad_Ad84 The Tick

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    No no, I agree completely. I often get called plenty of names for trying to do the same thing. People will follow a guide assuming it to be correct without much thought.

    I had assumed "all RGB moddable N64's" was sufficient, but you are right I should have been more specific. :)

    If you are in contact with the GameSX owners, they should change that snes jr guide.
     
  5. link83

    link83 Enthusiastic Member

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    Yes the GameSX guide needs updating, I am not in contact with the owners but since its a wiki I was planning to just edit it or add a new updated guide with RGB, S-Video and C-Sync (The guide is already half written in a word doc on my desktop)

    DarthCloud only recently discovered the C-Sync output on the 'S-RGB A' chip. I suggested to him that Pin 18 should be investigated further, as I thought it might be C-Sync output based on other ROHM video encoder datasheets, and DarthCloud used an oscilloscope to check and confirmed it was C-Sync.

    Nintendo never actually used this C-Sync output though, so without an oscilloscope or trial and error there is no way anyone could have known there was a buffered C-Sync output available on the chip. Whoever wrote the guide originally probably should have mentioned about buffering the signal though, but since it works fine without buffering people often only add whats absolutely necessary for things to work.
     
  6. Bad_Ad84

    Bad_Ad84 The Tick

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    Fair enough.

    I will change my wiring to the new correct method. Fortunately I didn't put it all back together yet.

    I guess the last piece of the puzzle is a DIY solution for the buffering, if you need to come directly off the VDC-NUS.

    Again, many thanks - this thread turned out quite enlightening.:thumbsup:

    Edit:

    Looking at Darthclouds schematic, it seems he already shows the parts for the C-Sync buffering. So all is well :)
     
    Last edited: Jul 24, 2011
  7. link83

    link83 Enthusiastic Member

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    Glad to help :)

    The N64 sync buffering circuit is almost identical to the one used on the SNES revision shown in DarthCloud's schematic, only with a few different resistor values.

    Basically there are six missing components on the NUS-CPU-04 revision, which are still present on the NUS-CPU-01 to NUS-CPU-03 revisions. On the NUS-CPU-03 N64 these components are:-
    R16 - resistor in series marked '102'
    R15 - resistor to ground marked '103'
    Q1 - ROHM transistor marked 'Z-R'
    R1 - resistor to ground marked '301'
    R14 - resistor in series marked '750'
    C22 - capacitor to ground - 47pF(?)

    If someone was really interested then I could also draw up a diagram as well, but I think most people dont experience any problems using Composite video for Sync, and if they do they often use an LM1881 circuit instead of rewiring their SCART cables :shrug:
     
    Last edited: Jul 24, 2011
  8. Bad_Ad84

    Bad_Ad84 The Tick

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    I have a LM1881 within my RGB to VGA convertor - As stated above, it still looked bad until I used C-Sync directly.

    We will see what the op's results are with his sync stripper.

    edit:

    I get no output when using pin18. Do I need to lift the pin?
     
    Last edited: Jul 24, 2011
  9. link83

    link83 Enthusiastic Member

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    I have a feeling your sync proplems are related to Nintendo's whole "Lets mess around with the PAL video circuit so that was can make PAL specific video cables and our customers will be forced to buy official PAL stuff!" Some people dont believe Nintendo would do this, but its well known that they 'region locked' PAL NES and SNES controllers, and NoE were fined a huge amount for price fixing in the 90's so...

    The 75ohm resistor to ground on Composite video inside the SCART cable should have fixed the sync problem for this French N64, but if anyone wanted to test if 'Nintendo's meddling' is actually the cause you could try cutting the trace/lifting the pin for Composite video coming from the 'S-RGB A' chip, and then adding the NTSC Composite video circuitry shown in DarthCloud's schematic (Only the 75ohm resistor in series and 220uF capacitor is strictly necessary) Then use a straight though connection on the SCART cables Composite video line. If this fixes the problem then its definitely Nintendo's meddling that is to blame.

    <EDIT> Hmm, I dont think you should have to lift the pin - pretty sure its not connected to anything(?) You can try if your confident you can solder it back again if need be (Dont want to be responsible for any harm coming to your N64 - even though Pin 18 is unused)
     
    Last edited: Jul 24, 2011
  10. Bad_Ad84

    Bad_Ad84 The Tick

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    I hand solder tsop48 upto TQFP100+

    Also own £1.5k IR BGA rework station.

    Dont need to worry about replacing it :)
     
    Last edited: Jul 24, 2011
  11. link83

    link83 Enthusiastic Member

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    Well, I say go for it then! You can always try the Composite video method mentioned in my previous post, or go back to the C-Sync input you are currently using (preferably adding in the buffering components)
     
  12. Bad_Ad84

    Bad_Ad84 The Tick

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    I will do some more work on it next weekend.

    I currently have a bunch of other paid work to be doing, I will report back with results when I have them.

    Edit:

    Lifting pin 18 and connecting to the lifted leg worked perfectly.
     
    Last edited: Jul 24, 2011
  13. link83

    link83 Enthusiastic Member

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    Great to hear :)

    Maybe Pin 18 is grounded underneath the chip? Will have to investigate...
     
    Last edited: Jul 24, 2011
  14. Bad_Ad84

    Bad_Ad84 The Tick

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    I measured the resistance between pin18 and ground and its not directly connected. But it is connected via something (resistor/other stuff).

    However, this console is going back together for some Zelda usage now. So thats me done for the time being :)
     
    Last edited: Jul 24, 2011
  15. link83

    link83 Enthusiastic Member

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    Yeah, I made a pinout of the chip a couple of years ago and was quite sure I labelled it as 'NC' (not connected) but now i'm curious!
     
  16. fathertime

    fathertime Rapidly Rising Member

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    Inside the scart cable there is a 75ohm resistor to ground and 220uF capacitor in series on Composite Video. Is that right? (It's a PAL Gamecube RGB cable being used on a USA N64 - you can see it in the first Scart Cable picture in the first post).
     
  17. link83

    link83 Enthusiastic Member

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    No NTSC Nintendo console requires external components on Composite video (i.e. inside the cable/plugs)

    I just took a look at your first post and can say that if you have used Method 2 from that guide with the 'internal boost' part from the bottom of the page then that will be the cause of your problems. It is strongly not recommended, and I emailed mmmonkey some months ago and he updated the guide. If you look at the top of the guide there are now links to better mods that use an RGB amplifier to give a much better picture. I am afraid there is no way to just 'join a few points' in the N64 and get a good RGB picture, you have to add components.

    The quote from GameSX which states "N64 RGB Cable components will depend on the mod performed" was written by me, and it means exactly what it says. Some amp designs will allow you to keep the 220uF capacitors inside the cable since they are needed for the circuit anyway (So no point in removing them) Other amp designs will expect a straight connection to the TV - you have to look at the amplifier schematic (of which there are quite a few) to determine whats best for your particular mod, although most expect a straight connection with no components inside the cable/plugs.
     
    Last edited: Jul 24, 2011
  18. fathertime

    fathertime Rapidly Rising Member

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    This package arrived :clap:


    Looks like you need to order the VGA cables separately so no testing just yet... :-(
     

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  19. fathertime

    fathertime Rapidly Rising Member

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  20. brainpann

    brainpann Site Supporter 2012

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    Did you mod a cpu rev 3 or rev 4? I have been doing some rev 4's (with THS7314) and they all suffer from the "hatch effect" but THS7314 seems to clean it up a little; at least it doesn't seem as pronounced while using it.
     
    Last edited: Sep 30, 2011

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