I've been using a Melzi (v1 I believe, with an Atmega644A) on my Mendel90 for several years now with Jumper 15 set to USB. It has suddenly dawned on me that I should be powering the Melzi from the PSU so I set the Jumper to VREG (the pins closest to the screw terminals) and tried heating the bed. It seemed to take a while so I checked the voltage at the terminal and it read 6.53V. It was at this point that I touched the USB cable and found it was very hot. Why is the heated bed being powered via the USB cable?
The extruder heats up using the PSU power regardless of whether JP15 is set to USB or VREG.
Could it be that my Melzi is a clone? I'd be pretty disappointed if it is because it came with a Prusa i2 kit from a reputable seller (RepRapKitStore) many years ago.
The extruder heats up using the PSU power regardless of whether JP15 is set to USB or VREG.
Could it be that my Melzi is a clone? I'd be pretty disappointed if it is because it came with a Prusa i2 kit from a reputable seller (RepRapKitStore) many years ago.