Customer question: What is the correct troubleshooting order when a used LED screen is black?
English explanation
Define the scope first: whole system, one processor output, one network branch, one cabinet or one module. Ask whether the screen is fully black, showing black content, very dim or reporting “No Signal.” Record the last known-good time and recent changes such as a power event, input switch, software update, cable move or configuration change. Check in layers. Confirm upstream power and protection with qualified personnel. Check the source computer, input resolution, frame rate and processor preview. Then inspect processor output, port indicators, fiber/RJ45 link, SFP compatibility, cascade order and port mapping. If the signal reaches the cabinet, check receiver indicators, correct RCFGX, HUB, ribbon cables and module power under the isolation procedure. Use a known-good short cable or one known-good cabinet for a single-variable test. Do not replace the processor, cables and receiving card at the same time. Do not repeatedly reset a breaker or ask an unqualified person to measure live voltage. Save the current configuration before any parameter change. The service conclusion should state what is confirmed, what is likely and what still requires a site or factory test. A short video can show the symptom but cannot prove every internal condition.
Service boundary
Power, electrical measurement and cabinet opening require qualified site personnel. —
