Pins 5 & 6 of IC2 and IC8-18021 are connected to Pins 9 & 10 of IC1-TL494. One of the drivers may have failed. Trace the connection from the header pins to IC2 & 8. I would point to the pins, but don't recall which ones are connected. They will be one or two pins from the left.
Once you find the pins, remove the solder so that the drive pins are no longer connected and check the TL494 for drive.