David constructed this circuit today using a uni-polar stepper motor IC (seen upper right) he selected and ordered earlier. This device, an Allegro/Sanken SLA7026M, is a high power (3.0 amp peak) controller. It does require a bit more support circuitry as it does not have a translator on board and the (step) truth table requires control of four inputs simultaneously to sequence each step. Initially, it appeared that the circuit was operating as the holding torque on the motor could not be overcome manually. We may have suffered a chip burn-out for unknown reasons as there is no further response; investigating now. The very large stepper motor seen in the upper left is out of an HP Laserjet 3si (a monster).
