A black box or "no signal" label on the switcher's input almost always comes down to one of four things. Check them in this order — it's faster than guessing.

  1. Power to the camera. Confirm the camera's own power/status light is on. Obvious, but it's the most common actual cause and the fastest to rule out.
  2. Cable seated at both ends. HDMI and SDI connectors can look seated but not be fully locked in, especially HDMI after being bumped. Reseat both ends — camera end and switcher end.
  3. Correct input selected on the switcher. Confirm the switcher input number actually matches the physical port the camera is plugged into — cables get moved during setup/teardown and mismatches are common after a stage reset.
  4. Format/resolution mismatch. If the camera outputs a resolution or frame rate the switcher input isn't expecting (e.g., a camera left on 4K when the input expects 1080p), some switchers show "no signal" rather than a scaled image. Check the camera's output settings match what that input is configured for.
If it's a run-and-gun swap Keep a spare known-good HDMI/SDI cable at the switcher position. Swapping the cable is often faster than fully diagnosing which of the four causes above it is.

Signal drops intermittently, not fully out

That's usually a cable run issue over distance (long HDMI runs are more failure-prone than SDI over the same distance) or a loose connector vibrating during the service. If it's a long HDMI run causing intermittent drops, consider converting to SDI with a converter, or using an HDMI active/booster cable rated for the distance.