The main board on the Original Prusa MK4 and MK3.9 is the xBuddy board. The xBuddy board has ten status LEDs.
The MMU overcurrent light indicates that the current through the MMU port is higher than 3.6 A.
The print USB overcurrent light indicates that the current through the print USB port (---) is higher than 0.5 A.
The heater fault light indicates an overcurrent through the hotend heater, higher than 2.8 A.
The current fault light indicates an overcurrent through the whole printer, higher than 15.5 A.
The service USB overcurrent light indicates that the current through the service USB port (---) is higher than 0.5 A.
The print fan cools the printed model as it lies on the print surface. The associated LED indicates that this is active and spinning.
The heatsink fan cools the hotend components, including the heatsink. The associated LED indicates that this is active and spinning.
The hotend heater light indicates that current is flowing through the hotend heater. During a temperature rise, the light is fully on, while at a stable hot temperature, it is expected to blink.
The main power LED indicates the presence of the needed voltage for the xBuddy to operate, 3.3 V.
The heatbed light indicates that current is flowing through the heatbed. During a temperature rise, the light is fully on, while at a stable hot temperature, it is expected to blink.
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