Video Troubleshooting
Most digital video failures are not broken hardware at all — they are conversations between devices that have gone wrong. When a source and a display connect, the display introduces itself by sending its EDID, a small block of data listing the resolutions, frame rates, and colour formats it can accept. The source reads that and chooses a format to output. If the EDID is wrong, missing, or quietly stripped out by a cheap adapter or an over-long cable, the source is left guessing — and it guesses badly, giving you no image, the wrong resolution, or a picture the display cannot lock onto. This is exactly why EDID managers and emulators exist: they present a stable, known capability to the source so it stops guessing.
HDCP is the other usual suspect. It encrypts protected content and insists that every device in the chain authenticate itself, so a single non-compliant splitter or converter anywhere in the path breaks the handshake and the screen goes black or throws an error — even though the cable itself is perfectly fine.
Because of all this, the productive way to troubleshoot video is systematically, following the signal flow. Confirm the source is outputting, then check each device in turn, then the display, and look hard at EDID and HDCP before you start swapping boxes. Far more often than not the gear is working exactly as designed; it is the negotiation between the boxes that has failed.
When video fails, check EDID before replacing gear.