Before I start, yes, I do have the jumper on J7 installed.
I set up a small motor connected to the terminal block, together with an external 3v power supply, all as described in the manual. (The motor works when connected directly to the batteries.)
When I run either "motor" or "potmotor" (in C or Python), neither activates the motor. After another look at the manual I tried connecting 3.3v and ground (from Gertboard pins) directly to the pins Mot A and Mot B in J5. Table 3 in the manual indicates that this should produce a rotating motor. My multimeter stubbornly reads 0v between the Mot A and Mot B output terminals whatever I try.
Connecting my motor/battery setup to the open collectors, running "ocol", everything works properly.
Can I conclude from this that the motor controller is dead? Or am I missing something?