I just installed the Extrusion Upgrade kit on my Ultimaker 2. Process went pretty smoothly... except after reassembly none of the motors would spin! First error I got was ER06 Z-Stop switch stuck. But the switch is fine, the problem was that the Z motor was not running. Playing with Pronterface I verified the bed heater still worked, but all three stepper motors did not move.
And also... the A4988 stepper drivers are all very hot on the PCB! Even when motors are not supposed to be running.
I conjecture that I burned out the drivers by manually sliding the print head and bed. This spins the motors pretty fast since they are geared up. I measured >50Vpp coming out of the motor while sliding print head! That might be enough to burn out the gates in the driver chips.
Anybody else see this happen?