No Video Signal Fix for CVI Format BNC Cameras

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  • When you install security cameras that output CVI (HD-CVI over coax / BNC) onto a new Viewtron hybrid DVR, the live view can come up black or every channel can say No Video Signal—even when those same cameras worked fine on the old recorder.

    How do I fix no video signal on a Viewtron security camera DVR when the cameras are CVI format?

    CVI is one of the common HD-over-coax formats (along with TVI, AHD, and older CVBS analog). Viewtron hybrids support all of them, and Auto under Camera Signal usually picks the right one. On some CVI cameras, Auto does not lock, so you have to set the channel to CVI/CVBS by hand under Edit Camera > Camera Signal.

    Important: only some Lorex BNC cameras are CVI and hit this. Plenty of Lorex BNC cams are a different format and come up fine on Auto with no change. The same fix applies to other third-party brands too—any BNC camera that actually outputs CVI can need Camera Signal set to CVI/CVBS when Auto misses.

    1. Confirm cameras and power first

    Before you dig into menus:

    1. Make sure each camera has power. Camera power is usually a separate 12V supply or distribution box from the DVR’s own power brick.
    2. Confirm the BNC video cables are seated on the back of the DVR (channels 1, 2, 3… matching where you expect them).
    3. If none of the cameras show any signal at all—not even a scrambled or wrong-color picture—double-check that camera PSU. “No Video Signal” with zero picture often means the DVR is not seeing anything on the input yet.

    Wrong Camera Signal on a live camera usually looks scrambled or wrong-colored. A completely dead “No Video Signal” on every channel is often power (or a cable) first—then the signal setting once power is solid.

    2. Open Edit Camera > Camera Signal

    From live view on the Viewtron hybrid DVR:

    1. Click Start (bottom left—same control you use to log in).
    2. Go to Settings > Camera > Edit Camera.
    3. On the left, open Camera Signal.

    That is the same Camera Signal page where Lite mode lives. Lite is a resolution / frame-rate tradeoff—different job. Here you only care about the Signal format for each channel.


    3. Set Signal to CVI/CVBS for those channels

    On the right side of Camera Signal you will see a Signal dropdown per channel (Auto, CVI/CVBS, TVI, AHD, and similar labels depending on firmware).

    1. For CVI cameras (some Lorex BNC / MPX-style models, plus other brands that output CVI), set Signal to CVI/CVBS for those channels.
    2. If they are all the same model, set every used channel the same way. If they are mixed brands or formats, set each channel to what that camera actually outputs.
    3. Click Apply and wait for the update to finish.
    4. Exit back to live view and check for picture.

    Still black after Apply? Try the other HD formats one at a time (TVI, then AHD) with Apply between tries—or put a known-good channel back on Auto if that channel was already working. You are matching the camera’s output, not “forcing Lorex.” Only the cams that actually speak that format need the change.

    4. If you get picture but scrolling / horizontal lines

    Once the signal format is right, you should get a steady color image. If the picture comes in with scrolling lines, fading in and out, or the monitor / recorder acting unstable, that is a classic dirty-power symptom—especially on an older shared camera power supply that has been through storms or years of heat.

    • Plug the camera power supply (and the DVR, if it was on a questionable strip) into a known-good wall outlet and retest.
    • If lines stay across several cameras that share one supply, you may need to replace that camera power supply / distribution box. You should not need to redo Camera Signal after a PSU swap—the setting holds.

    5. Quick checklist

    • Black / No Video Signal with CVI-format BNC cams on a Viewtron hybrid ? Start > Settings > Camera > Edit Camera > Camera Signal, set to CVI/CVBS, Apply.
    • Only some Lorex BNC cameras are CVI—plenty of Lorex cams never need this.
    • Other third-party CVI cameras (not just Lorex) can need the same Camera Signal adjustment.
    • No signal at all on every channel ? verify camera power first.
    • Picture OK but scrolling lines ? aging / weak camera PSU is the usual fix.

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