Gray Test Screen despite signal? (NTSC N64)

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    Question first, details to follow: Is something wrong with my console mod, with my SCART cable, my OSSC, my TV, or some combination of those? Or do I need more information first?

    Just got my NTSC N64 modded by oghugo, a modder with great reviews. I also purchased a “Super Nintendo SNES/RGB N64 sync-on-luma RGB SCART lead SHIELDED GROUNDED cable” (no link because I can’t find the exact same cable on their store anymore) from And, obviously, I got an OSSC.

    I plug it all together and do the following:

    —Turn on the OSSC. The gray test square appears correctly.
    —Tune the OSSC to RGBs (A/V1, setting 1).
    —Turn on the N64.

    And this is what happens:

    —The game audio comes through. Happy music!
    —The gray test square persists unchanged. It doesn’t blink, waver, or dim. Just a gray test square.
    —The LCD on the OSSC says “no sync”.

    What I know so far:

    —This happens on two TVs (a Vizio and a Samsung)
    —Sega Genesis works great on same setup (also got that SCART cable from retro access)
    —It’s like this for multiple games

    I’m under the impression the screen should display something when I turn on the N64, even if just a flicker or something. Do I need more data to guess at what’s going on? Thanks in advance!

    P.S. Bonus detail: I can’t find the exact cable I purchased from retro access (otherwise I would have linked it above). They are currently selling this cable, which is vinyl braided (mine is not) and I’m pretty sure the write-up was different, but I can’t remember how. So I’m worried it’s the cable for that reason, but I obviously don’t know, that’s why I’m here! 🙂 Thanks again!


    sounds like your N64 isn’t outputting luma at all, can you connect it to a display using S-video and does that work?


    Thanks for the reply. New development: I connected the N64 to a display using S-video and it works perfectly. So, the console is outputting luma. Could the problem be that the console isn’t outputting R and G and B? Or is the problem probably just the scart cable?

    Related question: Can I trust this OSSC, since it upscales my Genesis signal perfectly? Or is that ability unrelated to the ability to upscale N64 signal?

    Thanks again.


    I don’t think there’s a known incompatibility that could make the OSSC fail to pick up a sync-on-luma signal from the N64. You should contact the modder. They should be able to tell you what cable works with your console. Sync-on-luma is probably a safe bet, though. You could check that the cable is actually wired for sync-on-luma.


    Absolutely, you can reasonably assume your OSSC is working if your Genesis is working.

    Without knowing the modders work it’s difficult to speculate, try slowly increasing the Analog Sync Vth and the Vsync Threshold on the OSSC.


    If S-Video is working then the OSSC should sync with a luma sync RGB cable even on a unmodded console. Check your cable. Another user on this forum received a cable from the same seller where sync and ground were reversed.


    Update, in case any future people want to know how this resolved: Turns out the cable vendor accidentally sent me a csync cable rather than a luma cable. They sent me the correct cable and all is now working great on my Vizio m50-c1.

    Thanks everybody for your help!

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