I have recently been using your A4988 boards to power a set of stepper motors for a mendel reprap using sanguinololu electronics.
While testing today we noticed at the start of the day that the extruder stepper would jar at its position and not turn around, we reset the machine, replugged the motors and flashed the eeprom and everything seemed to work ok.
Later on the same thing happened to the motor driver, this was checked by swapping motors and boards around and was found to be the stepper driver. We used a scope to check the STEP pin and this was functioning correctly.
The output of the stepper driver when ‘stepped’ would only change for 3 of the output pins; one of them would remain static throughout any stepping moves. This was verified as the output pin from the board and the socket coming out of the main circuitboard read the same. We also checked the other outputs for dry joints and resoldered most of them to no avail.
We used a small brass pulley as a heatsink and this seemed to get pretty hot over the day.
Has this motor burned out? Might it just work again another day? Interference? Any ideas on what might be happening?
Any help would be amazing