Hi,
Finally I replaced the original board from prusa i3 with reprap board.
I Installed latest marlin firmware from git, and on c the pronterfce application.
All tweaks, homing and tuneup on axis and feeder are OK. +/- .0. 1 10 mm are fine.
All good, except few things.
- The board works only if Is powered from it's power supply and the USB plugged to a 5V USB power or computer.
- Printing several models (from pronterface / or menu Sdcard) including test cube, results in failure.
- The filament does not feeds during the print. Does not move at all. The steps/mm was tuned up properly.
- I can force the extruder form the pronterface back and forward without problems.