Woohoo! It lives, Igor!
I did wonder why the tests to turn the motor an entire revolution weren’t actually turning the spindle very far until I remembered that it has a 27:1 gearbox on. Easily missed, that one 🙂 And I have the buttons cross-wired as compared with the LEDs, but that’s just a question of switching a connector around the other way on the pin header I think. And the buzzer now works, though I don’t recall actually doing anything to fix that.
So now I need to decide which telescope I’m going to put it on and make up a suitable bracket. Then probably re-balance everything thanks to hanging another half kilo of motor on the end of the OTA.
Oh, I almost forgot — need to adjust the current limiting resistor on the stepper driver board too.