@hendo420 said in Voltage drop on Duet Wifi when connecting 7" PanelDue:

I was reading through the forums, I didn't realize I could just use the 4 pin connector and not the ribbon cable to use the LCD. So I removed the ribbon cable and only attached the 4 pin connector and all is working. So this means I just can't use the sd card slot on the PanelDue.

It sounds like there is a short in either the ribbon cable, or a problem with the SD card slot part of the PanelDue. If the Duet still works properly when the ribbon cable is plugged into the Duet but not into the PanelDue, then the fault is in the PanelDue.

Assuming the Duet does work with the ribbon cable connected to it but not connected to the PanelDue, one obvious thing to check is that there are no solder bridges on the back of the ribbon cable socket on the PanelDue.