N64 RGB Mod - Poor quality image

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

  1. Bad_Ad84

    Bad_Ad84 The Tick

    Joined:
    May 26, 2011
    Messages:
    8,605
    Likes Received:
    1,376
    Thats awesome, because it will work on all consoles - not just the easily RGB modded ones.
     
  2. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    I have a NTSC N64 with pcb NUS-CPU-03, that means i have all components for c-sync. I did the rgb mod using ths7314. On my old crt it looks great with no difference if i i use composite or c-sync.
    But on my 40c8000 led 3d tv i have problems. If i use composite the image is like looking through a net. If i use c-sync, the image is out of sync. what should i do?
     
  3. APE

    APE Site Supporter 2015

    Joined:
    Dec 5, 2005
    Messages:
    6,417
    Likes Received:
    141
    Have you tried using a sync stripper instead of c-sync?
     
  4. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    I don't have one.
     
  5. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    How are you wiring sync? Sync has a specified signal level--approximately 0.3Vpp into 75 ohms.
     
  6. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
  7. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    So basically you're cutting composite video and wiring composite sync to it? Where is composite sync's source? The DAC chip? The info on that page seems dubious since RGB is not built in so why would the connector provide sync. If you had to wire the DAC to the sync pin/composite pin, the DAC's output level must be checked. Following common convention the DAC will probably output 0.6V expecting there to be a series 75 ohm resistor forming a voltage divider with the 75 ohm resistor in the TV, which would mean you would need to add one if it's not already present on the board. This is speculation because it's possible for the DAC to internally terminate the cable, but it's unlikely.
     
    Last edited: Oct 6, 2011
  8. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    pin 14 of the dac is c-sync. if i use it i get an image, but it's too dark. i used an 75 ohm resistor on c-sync pin of multi-out port and it's working but again the image it's too dark.
    after that i used a 75 resistor on composite and now the brightness and colors are perfect on both crt and led, but i still have the "net" problem on led tv.
     
  9. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    I don't understand that because sync has nothing to do with the picture brightness. I also don't understand how you're both using composite video and composite sync. RGB configurations will use one or the other (composite video for SCART, composite sync for everything else). Since you claimed composite video looks like a net, perhaps you're accidentally viewing composite video via SCART?
     
  10. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    I'm using composite and sync one at a time (to test wich one is best). I'm not accidentally viewing composite video via SCART (i know because if i desolder red, the picture will not have red).
    Well, it seems that on this led tv the c-sync has something to do with brightness. For example i made an rgb amp for the pc engine like this:
    http://www.gamesx.com/grafx/pce_rgb.jpg

    old crt - beautiful image. led - very dark picture. i remove the amp from the sync and now the image is nice and bright, but sometimes goes dark for less then a second.
     
    Last edited: Oct 6, 2011
  11. Calpis

    Calpis Champion of the Forum

    Joined:
    Mar 13, 2004
    Messages:
    5,906
    Likes Received:
    21
    Those amps are "voltage followers" (current amplifiers) and in that configuration the signal output level (voltage) is always lower than the input so naturally the picture will be darker, and in this case about half brightness assuming the display doesn't have gain control. Each console has different ideal amplifiers due to varying output levels.

    It's my guess you don't need an amplifier at all, much less one of these dogmatic circuits. I'd put a series 75 ohm R and 220 uF C on the DAC outputs and see if it can directly drive the line, I think it does for composite video afterall...
     
    Last edited: Oct 6, 2011
  12. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    Problem solved. I used as sync pin 7 from the multiout (luma) and a 75 R and it's working great. No more net effect and the colors and brightness are excellent. While i had the n64 open i cut the 5v trace from the multiout and connected 12v and in the scart i used a 560R between pins 8 and 16 and now the tv auto-switches to rgb 4:3.

    As a side note, i also used a 75R in pc engine on c-sync and now no more problems with the brigthness.

    Thax Calpis for the 75R tip.
     
  13. fathertime

    fathertime Rapidly Rising Member

    Joined:
    Jul 14, 2011
    Messages:
    82
    Likes Received:
    0
    Sorry to dig up this old thread but I too have this slightly dark screen problem using the c-sync hack (cut composite and link the pins on the multiout port). The R, G and B lines are amplified through the THS7314 chip and it is a bright stable picture with composite sync (however with the X net pattern). Using c-sync the image has no X net pattern but I must admit that it is a little dark. Picture attached.


    Tonight I put a 75ohm resistor in series on the C-sync line after reading your comments but no change.. I just turn the brightness up to 100% though you can still notice it on dark games like the ghost house in Mario64.

    Can you tell me more about this method of getting a bright picture if one has already modded using using the THS7314 and C-Sync with the PAL Gamecube Scart cable?

    Many thanks!
     

    Attached Files:

  14. fathertime

    fathertime Rapidly Rising Member

    Joined:
    Jul 14, 2011
    Messages:
    82
    Likes Received:
    0
    Hi Gorgyrip, I re-read your post and see now that you are actually using the svideo Y luma pin 7 instead of the c-sync pin and linking that to the cut composite video pin for sync. You also have a 75 ohm resistor (in series I assume?)

    So anyway, I've done this and left the THS7314 amp on the R, G, B lines in - but now the picture is too bright!! (see attached pic)

    Did you take the THS7314 amp out? So close to getting this resolved once and for all...
     

    Attached Files:

    Last edited: Oct 14, 2011
  15. fathertime

    fathertime Rapidly Rising Member

    Joined:
    Jul 14, 2011
    Messages:
    82
    Likes Received:
    0
    This is like the 3 bears. First one was too dark, second one was too bright, but if I use a PAL SNES RGB Scart cable, it's just right :dance:


    To anyone looking for "the perfect RGB mod" for N64, it's like this:

    i) Amplify the RGB lines with the THS7314 chip (as per http://mmmonkey.co.uk/console/nintendo/ntsc_nintendo_64_rgb_new.htm)

    ii) Then cut the composite video sync trace (PIN9 on the multiout marked V) and run a wire with a 75ohm resistor in series from PIN7 on the multi out (marked Y) to PIN9. (almost like this http://mmmonkey.co.uk/console/nintendo/rgbntsc.htm#link83 but linking 7 and 9 with an added resistor instead of 3 and 9)

    iii) Use a PAL SNES RGB Scart Cable (see the first post of this thread for a picture of that) - PAL Gamecube cable is too bright.


    I guess that means those of you with REV04 boards with no c-sync on PIN3 can simply use the PIN7 instead with no need to rebuild the c-sync circuit...

    Thanks to gorgyrip & Calpis for the help.
     

    Attached Files:

    Last edited: Oct 14, 2011
  16. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    Sorry, i didn't see your posts. The problem was also your cable. Like i said, i used ths7314, and as sync i used luma and a 75 resistor. You did the same. The scart cable has nothing inside (no resistors or capacitators), only one resistor between scart pins 8 and 16. i'm glad you solved your problem.
     
  17. fathertime

    fathertime Rapidly Rising Member

    Joined:
    Jul 14, 2011
    Messages:
    82
    Likes Received:
    0
    Thanks for that info. I actually took the internal 75ohm resistor out of series on the sync line and now both the PAL SNES and PAL Gamecube cables work fine (they probably already have the 75ohm in series within the cable). The image is perfect.

    All of this has been on a REV03 console but I have a REV04 console here too so I'll order another THS7314 and see can that be modded using the luma sync line.

    Thanks again.
     
  18. gorgyrip

    gorgyrip Gutsy Member

    Joined:
    Oct 26, 2007
    Messages:
    450
    Likes Received:
    16
    yes, pal snes and pal gamecube cables have inside the resistor.
     
    Last edited: Oct 15, 2011
  19. brainpann

    brainpann Site Supporter 2012

    Joined:
    May 1, 2011
    Messages:
    403
    Likes Received:
    6
    I just tried this on a rev 04 with the THS7314 amp installed and it worked perfectly. No more "hatching". Many thanks to everyone for all the info!
     
    Last edited: Oct 16, 2011
  20. ApolloBoy

    ApolloBoy Gutsy Member

    Joined:
    Sep 22, 2011
    Messages:
    425
    Likes Received:
    0
    I just attempted an RGB mod for my N64 and now it seems to have developed an odd audio problem. When I was testing it with the RGB mod, I got loads of static through the audio (almost like what happens when a game glitches up) that occurred whenever there was audio playing. I removed the RGB mod and now I'm still having the audio issue. What could cause this to happen? I inspected the system when I removed the RGB mod and I didn't see any broken traces or the like.
     

Share This Page