ok I replaced the z-axis stepper driver with a new one and the movement system works now
but now I have another problem when assembling the heat bed the thermistor fell off and I resoldered it
and the temperature is now a little off but still proportional
So the temperature for the bed is now about 6 Degree Celsius when in reality it is 24 degree Celsius
I have the idea to load a new firmware to the sanguinololu with another settings for the resistor
but when I want to upload the firmware arduino 0022 says
stk500_recv(): programmer is not responding
The solutions from the sanguinololu wiki page do not work in my case
even other versions of arduino like 0023 or 1.00 do not work