Fixed Stepper motors missing some steps

[kasey 0]

Hello,

I have an simple head Ultimaker with a pcb 1.5.6, flashed with the last firmware (UM-v1.1-PCB1.5 115200) but I encounter an issue with my steppers. When I start an extrusion, after some seconds, the steppers miss many steps and do very stange songs, like if the uC was submerged by some interrupts.

I have made a movie to explain that :

http://forge.kasey.fr/movies/ReplicatorMotorDriverIssue.mkv

I have :

• 
  [*:1o741sty] checked power supply, I have a continuous 19.6 v
  [*:1o741sty] try replicatorg, printerface, Ultimaker hardware controller
  [*:1o741sty] check connectors
  [*:1o741sty] double flashed the Arduino 2560

Somebody have an idea for the origin of my problem ?

[kasey 0]

Ok, I have found the problem, the steppers was overheating. Cf :

http://wiki.ultimaker.com/Electronics_b ... or_drivers