I've built this design and also the Posix board... but I can't get Salvado's design working. Tested all components, replaced the PCB!, reprogrammed PIC and used 16F84A and 16F628 with no change and triple-checked stepper wiring connections and replaced all transistors. I still get noise or what seems interference/feedback when driving the motor. Here's a video example of one of my boards that work perfectly and one that doesn't. I really would prefer to get Salvado's working... better transistor placement and onboard 7805 is a real bonus.

Salvado Design Board with 470 resistor mod.. Motor has glitchy steps:



Posix Design Board... same schematic as above... motor is smooth:



I know there has to be a difference between the two board designs, but I'm completely at my wits-end to see what it may be. Any ideas on what to look for?