I've got a simple robot using a SN754410 to drive two small DC motors. I have 4xAA batteries supplying power to the motors through the motor power pin.
The motor driven from the pins on the right side of the SN754410 stops and starts properly.
The motor driven from the pins on the left side of the SN754410 run constantly. When my robot receives a command that operates this motor, the motor (already running) perks up and is more active for the duration of the command. This seems to happen regardless of what's happening with the motor logic pin on that side.
Any ideas? I've looked for soldering mistakes around the SN754410 pins but can't find anything that looks like it'd be shorting out.