Lulzbot Mini - Connectivity Issue Between Print Frame and Nozzle

General
1

My Lulzbot Mini started failing homing recently and I measured no detectable connectivity between the nozzle and the homing washers. I started probing wires and deduced that the print frame under the glass plate isn’t connected to the main frame of the machine and hence not grounded with the control board. I traced the grounding wires and found out that the brown grounding wire from the print frame to the main frame has a TVS diode on it that is blocking all connectivity and preventing proper grounding. It’s a 1N6373 TVS diode that I assume has failed, otherwise I’m not sure why there isn’t any connection.

Does anyone have any advice on this? Should I replace the diode or bypass it altogether? Is this due to another issue entirely?

Edit: the other wire that comes from the grounding on the print frame is a white wire that goes to the “x-min” connection on the board.

2

You should measure continuity from the nozzle to ground. You should NOT measure continuity from the washers to ground. The washers should connect to the Zmin.

The way it works is that when the nozzle touches the washer, it ground the Zmin input and the controller reads the touch. If the bed were grounded as well, it would always measure that the nozzle is touching the washer.

The purpose of the TVS diode is to provide a path for electrostatic discharge to go from the bed to ground without having the bed connected directly to ground.