DC500 4K FUSER No Display but All LEDs On – Signal Output Troubleshooting Guide

During installation of the DC500 4K FUSER, some users may encounter a situation where all four indicator LEDs are illuminated, but the monitor remains black with no image displayed. From a factory engineering standpoint, this status is important because it confirms that the device has already completed basic hardware detection.

In this condition, the fuser has successfully recognized the monitor as well as both connected systems (main PC and secondary PC). The issue is not a power failure or device damage. Instead, it indicates that the output video signal is not being accepted by the monitor, often due to timing, refresh rate, or initialization behavior.

Based on factory validation tests and field installation feedback, this behavior occurs most frequently during first-time setup, monitor replacement, or when the display previously operated under a high refresh rate configuration.

Common Causes Identified

-The monitor fails to lock onto the initial output signal

- Output frequency exceeds the monitor’s supported range

- Abnormal EDID data cached by the monitor

- Incompatible output timing mode during startup

Verified Solutions (Recommended Order)

1. Reset the FUSER
Press and hold the K3 button for 5 seconds to reset the device. This clears temporary signal parameters and forces a fresh output negotiation.

2. Perform a Full Power Cycle
Power off the monitor and disconnect all cables from the fuser. Reconnect all cables securely. Power on the monitor first, then power on the fuser during the monitor’s startup phase.

3. Restore Monitor Factory Settings
This step is especially important for monitors that have been used with custom resolutions or high refresh rates. Factory reset restores default EDID behavior.

4. Switch to B Mode
Press and hold the K1 button for 5 seconds, then release. The device will switch to B mode and automatically reboot within approximately 20 seconds, using an alternative output timing profile.

In the majority of cases, these steps restore normal display output. If the screen remains black after completing all procedures, the issue may be related to resolution limits, refresh rate locking, or EDID handshake behavior, which will be addressed in separate technical articles.

For stable operation, always ensure the monitor supports the required resolution and timing specifications before installation.