One DC transformer pluged in the external plug of the printer: the one with is linked to the on/off switch and to the Ramps. The normal way to power the printer.
When I use it, I have "Minterm" error, SD reader is not recognized but fans are working and when preheat, I can feel temperature on the extruder head. No way to move steppers and no recognition of their coordinates.
If I try something quite different. If I plug the (same) DC transformer directly on the Mainbord (mega 2560), then:
- no minterm error, no fans
- temperature and X,Y,Z coordinates are ok
- SD redaer is ok and I can read (ok, only 4%) of the file on it
- X, Y ,Z coordinates are acquired
- no way to move steppers anyway
It looks like (only my feeling) that the Ramps doesn't correctly supply power to the 2560... but I can't see why...
(power supply (DCtransformer) seems ok and gives 12V)