N64 RGB Mod - Poor quality image

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

  1. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    You don't understand, with that barebones circuit you ARE inappropriately wiring the TV directly to the LM1881--the CSYNC output is connected directly to the TV--the signals are not remotely compatible as-is.

    LM1881's CSYNC logic output: digital, swings 3.0 V at the output (3.0 V gets delivered to the TV input), meant to drive multiple 100k ohm logic inputs, <20 ohms output resistance meant to drive low-capacitance PCB traces, low constant current capability

    True TV sync output: bi-level analog, swings 0.6 V at the output (0.3 V gets delivered to the TV input), meant to drive a single 75 ohm TV input, precise 75 ohm output resistance meant to drive high-capacitance 75 ohm coax cable, high constant current capability

    See the difference?

    With your XM29 you can turn off the 75 ohm input terminators (it will instead be 1K ohm or so), that would be the thing to do here if you aren't going to build a proper circuit. That way at least the DAC is protected (or the redundant LM1881, if you choose).
     
    Last edited: Nov 2, 2013
  2. robneal81

    robneal81 Site Supporter 2015

    Joined:
    Sep 25, 2012
    Messages:
    15
    Likes Received:
    0
    You're right, I genuinely don't understand (no sarcasm, I'm being serious). I really do appreciate your help, but I'm not sure if I'll ever truly "get it"...but I may not need to, in order to solve my problem. Could we dial it back a bit and keep it simple:

    - I have a few consoles that aren't working with my current setup, others work perfect.

    - If I route the ones that don't work through a Sync Strike before I plug it into my monitor, they work flawlessly.

    - One solution would be to route all the consoles that don't work through one switch, into my Sync Strike, into the monitor. That would work perfect, except I'd much rather only use one switch.

    - I'd much rather work on getting compatible sync from each console: That's what I'm asking for help with. If I insist upon dealing with each console individually, what's the best way to accomplish that? Do I keep playing around with my N64's, trying to find a compatible sync, or do I just build a circuit between composite video from the console and sync to my cable (essentially doing the same as putting a sync strike between each console and my switch)?
     
  3. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    Every console is different. Some provide digital sync signals, others do not. When you have access to a digital sync signal, as you do with the N64, the best solution is to build a sync driver circuit. This sync driver can be as simple as a 680 ohm resistor; though electrically it's not ideal, in practice with short cables you can probably get away with it. For the consoles with only an analog c-sync, such as the PCE apparently, you can either use a sync stripper, then follow that with a digital sync driver, or it can be level shifted and amplified with an op amp (more complicated but better signal quality).
     
  4. beanieboy182

    beanieboy182 Member

    Joined:
    Apr 3, 2014
    Messages:
    13
    Likes Received:
    0
    i have a french n64 fra-001 and used the cut trace to pin V (n64 board) and wire from theBA6596F S-RGB A chip to get red green blue (with 75ohm resistors) and csync (actually ended up leaving it on the Y Luma (pin 17) but either that or pin 18 csync didnt change the quality on my 55" LED tv
    i would say its pretty poor quality
    i think my snes looks better quality using the same cable mind
    anyone have this problem of bad quality after using RGB mod ??
    it doesnt look much better than composite to be honest.
    i will try and get some pics but its hard!
     
  5. beanieboy182

    beanieboy182 Member

    Joined:
    Apr 3, 2014
    Messages:
    13
    Likes Received:
    0
    can someone verify this is the quality i should be looking for or is this chuff ?
    IMG_1357.JPG
    this would be the end of the sniper rifle of goldeneye
     
  6. lolzvid

    lolzvid Peppy Member

    Joined:
    Jan 27, 2012
    Messages:
    340
    Likes Received:
    11
    STOP. BUMPING. OLD. POSTS.
     
  7. ApolloBoy

    ApolloBoy Gutsy Member

    Joined:
    Sep 22, 2011
    Messages:
    425
    Likes Received:
    0
    At least he's not as bad as ShadowZero (yet).
     
  8. ShadowZero

    ShadowZero Spirited Member

    Joined:
    Apr 18, 2013
    Messages:
    136
    Likes Received:
    9
    <3

    (re-using old topics > spamming new ones)
     
    Last edited: Apr 4, 2014
  9. beanieboy182

    beanieboy182 Member

    Joined:
    Apr 3, 2014
    Messages:
    13
    Likes Received:
    0
    Sorry i have made my own now :D
     
  10. Bad_Ad84

    Bad_Ad84 The Tick

    Joined:
    May 26, 2011
    Messages:
    8,594
    Likes Received:
    1,372
    STOP. BEING. STUPID. It makes sense to post in this thread, rather than make another one. Now you have 2 threads, which if his gets resolved - means we have the information split between 2 threads, rather than just one. Making it HARDER for other people to find/use.
     
  11. bacteria

    bacteria I am the Bacman

    Joined:
    Apr 8, 2008
    Messages:
    978
    Likes Received:
    61
    Only RGB mod i've tried is the one from Otakis, and only screen i've tested it on is for my current multi system project using an 8" JoyTech PS2 screen; output is top rate and has no issues with image quality.
     
  12. ApolloBoy

    ApolloBoy Gutsy Member

    Joined:
    Sep 22, 2011
    Messages:
    425
    Likes Received:
    0
    So you do it just to troll then, okey doke, totally understand now.
     
  13. ShadowZero

    ShadowZero Spirited Member

    Joined:
    Apr 18, 2013
    Messages:
    136
    Likes Received:
    9
    ApolloBoy, how old are you? Maybe that puts matters in perspective to me (and that's a serious question, people just think differently on different ages). I do not troll, I post on topic, and for that I rather re-use existing topics than spam new topics. If anybody trolls, it seems to be you (towards me in this case, 2x).

    Just like Bad_Ad84 said:
    I just can't understand people on fora don't understand that.
    But now I've taken it off-topic myself (apologies for that), so if there's anything else to say I suggest to continue in PM.
     
  14. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

    Joined:
    May 13, 2007
    Messages:
    553
    Likes Received:
    285
    One thing I've noticed on this RGB mod is that the video is pretty dark. I knew it but didn't think much of it until Voultar pointed it out to me earlier, as his is the same way, and he found a comparison video (https://www.youtube.com/watch?v=tHwxu-3JwhE) that clearly shows that on composite, the picture is much brighter. I am using the standard THS7314 amp which pretty much everyone else is using. Does anyone have any input on how this could be rectified? He was thinking perhaps pull-up resistors on the RGB lines?
     
  15. Bad_Ad84

    Bad_Ad84 The Tick

    Joined:
    May 26, 2011
    Messages:
    8,594
    Likes Received:
    1,372
    Doesnt look brighter to me at all?

    There is always a slight different between how the image looks in RGB vs Composite vs S-video
     
    Last edited: Jul 7, 2014
  16. darcagn

    darcagn Site Supporter 2013, Site Supporter 2014

    Joined:
    May 13, 2007
    Messages:
    553
    Likes Received:
    285
    Left is RGB, right is composite. That's when the Nintendo logo fades into the Mario Kart 64 logo. That doesn't look off to you? It's supposed to be completely white.

    When I get off of work later I'll take some caps of my own via RGB/S-video/Composite and compare

    Screen Shot 2014-07-07 at 6.30.21 PM.png
     
    Last edited: Jul 7, 2014
  17. Turrican3

    Turrican3 Member

    Joined:
    Nov 10, 2015
    Messages:
    21
    Likes Received:
    0
    Hi guys, I have issues with an RGB-modded japanese N64.

    Basically I see *lots* of horizontal stripes/noise when there's a bright-coloured image on screen; it's almost un-noticeable with a dark background but anything different than that will more or less show the issue.

    Any suggestions for things I have to look at? Or am I dealing with permanent damage?! (hopefully this is NOT the case)

    PS: at first I thought it was an issue caused by the sync separator circuit I'm using for the monitor connected to the console, but then I tried with a direct connection to a SCART-capable TV and, unfortunately, the horizontal stripes are there as well. :-\

    PPS: right now I don't know the exact details of the mod, but I can easily investigate if necessary (I think I can disassemble the chassis relatively easily)
     

Share This Page