Multi-projector troubleshooting requires identifying the source of a visible or operational problem before changing projector settings. This multi-projector troubleshooting guide explains how to diagnose image misalignment, focus differences, visible blend seams, brightness mismatch, black-level variation, gamma and color differences, signal loss, control failures, thermal warnings and projector replacement issues. By separating physical, optical, geometric, photometric, signal, control and environmental causes, technicians can troubleshoot professional multi-projector systems more systematically and avoid unnecessary adjustments that may create additional problems.