Issues with 'official' RGB modded N64

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    Hi guys,

    I got my OSSC last week and so far I’m quite happy with it.
    Works perfectly so far with my SNES and GameCube; however, my RGB ‘official’ modded french N64 is giving me some troubles :-/

    If I connect my N64 via the OSSC to my TV, the picture stays mostly black. Sometimes however, I’ll get a picture for a few seconds only for it to disappear again. A video of this can be found here:

    While trying to find the cause of the problem I noticed that the OSSC LED-display was rapidly oscillating between “313p 49.83Hz” and “312p 49.99Hz”. A video of this can be found here:

    At first I suspected the RGB cable; however, the same cable produces a beautiful, stable picture when I connect it to my SNES.

    I then tried to connect the N64 via the OSSC to my PC monitor. There, I get a constant picture. However, the picture is pretty unsteady.
    Nothing you’d notice during gameplay but especially in menus this gets quickly annoying. I also made a video of this effect which can be found here:

    Does anyone have any clues as to why this happens?
    Help is highly appreciated.


    It seems your N64 has an unusual sync signal. Can you tell me who modded it and which method was used?


    Try setting H-PLL pre and post coast to 3, and then increase Hsync tolerance. Tweaking analog sync Vth could also help. Which cable do you use btw?



    I was about the report possibly the same issue.

    My setup:

    – OSSC firmware 0.73
    – Optoma HD26 video projector (my only HD “TV” to try with)
    – Original RGB SCART cable from my SNES

    This is the setting that happily works with all of my retro consoles, at last the ones outputting RGB on the SCART of course. The cable in particular is being used with the SNES for a week, and the OSSC never failed me even after hours of playing.

    Now I have a Nintendo 64 NUS-001 (FRA) modded for RGB output. This is the actual modded console I bought, for technical details: (it’s the French store but the seller is also using English).

    At first, I was afraid because OSSC didn’t output anything and my old CRT displayed a distorted picture. But the modder told me I had to cut a wire he installed for modern displays. Indeed afterwards my CRT displayed a sharp picture but still not the projector.

    Then I tried with a PC monitor and it worked, except for small loses of the picture, but anyhow the OSSC is outputting a picture.

    Now I’m trying to figure out what’s wrong with the projector it was intended for.

    At turning on the OSSC with default settings, I get the test screen and when I switch to AV1 input with the remote, sometimes I get the picture from the game, with correct colors but shifted somehow and “scrambling”. It’s very brief so I recorded it:

    With default settings, the OSSC LED is green and the LCD displays: “AV1: RGBS 313p 15.62kHz 49.92Hz”.

    With the info button, it displays: “Vmod: 288p LO: 626 VSM: 0”.

    I followed your indications above and increased H-PLL pre and post coast to 3, even 5. I also increased Hsync tolerance by steps of 10 us until I reached the maximum. I also increased and decreased analog sync Vth. The projector is always like trying to find a picture and fails with “no signal”.

    The OSSC LDC displays the same information as with the default settings.

    I also tried the other options in the menu, restarting the OSSC to reset settings as necessary to avoid changing too many things at the same time and not knowing what could work.

    The projector only got HDMI inputs so I have to use a DVI-to-HDMI adapter. I guess it’s just a passive device joining electrical pins together.

    What could I also try? Except for “another TV”? 🙂



    By the way, I don’t think the projector is really that picky, because line triple mode works with it.


    Hey, I do have modded a French N64 with the same method…

    Modding work

    Unfortunately, I wasn’t my N64 but I remember that I have tested the work over the OSSC, too. It behaved as like as the other consoles on my TV set. So it might be your TV which has the problem…


    I saw this exact problem with my RGB-modded N64 on my OSCC when I used a sync-on-composite EuroSCART cable (even though my launch N64 supports composite sync). Switching to a sync-on-luma EuroSCART cable cleared it right up.


    Thanks ShootTheCore for the hint. I was tempted for quite a time to try these so-called retro cables. Would you recommend a manufacturer or store? Since this would be the standard Nintendo plug on the other side, would it also benefit to a SNES or GC picture quality?


    @ShootTheCore, @oursique: do you both have the symptom shown on the second video, i.e. mode changing rapidly on character LCD?. You probably have tried setting sync LPF to 2.5MHz, right?

    : do you have details of this mod? If I recally correctly, it was just about adding a couple “missing” SMD components to their place. I take that big zener diode (?) in the picture is to bring down 12V status voltage output to a lower level to prevent damage in case a c-sync cable is plugged in – right?


    @marqs, it’s changing mode (or rather losing sync) regularly but not what I would call rapidly. Here is a record with default settings where I boot the N64 at 0:04:

    I tried sync LPF at 2.5 Mhz (after the video is recorded), then also changed H-PLL pre and post-coast to 3, I also increased analog sync Vth by steps of 10 us but never got a picture.


    I wonder if your rgb-scart cable has 75ohm resistor to gnd on composite line as intended for PAL N64. If you still have original av cables, try hooking composite to green RCA on AV2 and see if you get stable sync (and B/W output).


    Oursique-I picked up my sync-on-luma cable from

    Marqs-sorry, I didn’t look at the OSSC display at the time, and I no longer have the same modded N64 to reproduce the sporadic syncing glitch I had with the CSYNC cable.


    @marqs Sorry I didn’t come back earlier. This the original RGB cable from the French SNES, I can’t tell and I’m not eager to crack open it.

    I tried the original composite cable, well I tried both of them because the composite cable from the GameCube was there too and I couldn’t tell them apart.

    I tried both AV2 modes and none have a stable sync. Both display “AV2: RGBS 313p 15.62kHz 49.92Hz” on the LCD.

    But the way, I tried a luma as sync cable I bought on for my SNES but it doesn’t change anything. No luck either with the comp as sync cable I bought for my GC.


    I see. According to this post there’s only one French PCB revision that supports easy rgb modification, so it’s quite strange if borti4938’s board worked without issues. Apparently multi-av pin 3 on that board is composite sync (that diode seems to be just esd protection then), so that could be something that made the difference for him. Still, it’s quite hard to believe cvbs/luma signals were so bad that stable sync could not be recovered even with all the filters.

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