Ok .. going to have to say it... Your motors aren't plugged in!

Just kidding, I know, I'm so funny. Good to see you again, you have the 14th ever PolargraphSD 🙂

Well, they are all good signs. 7.5v has always been plenty enough for me in the past. If you measure the voltage between the two pads/holes marked + and GND on the lower right-hand corner of the board, immediately to the right of the motor terminal socket.

If you want to check for continuity through to the stepper drivers themselves, the bottom-left corner pin of each stepper driver breakout board (just the board, not the chip itself) is the motor power supply pin, and the top-left is GND. So you can check the voltage between those two, but be careful not to short the power to the next pin along.

Next thing - make sure the bottom of the motor terminal connector isn't shorting against the USB socket on the arduino.

You could try sensing a voltage between some of the motor connector pins, but I wouldn't be very surprised to find that it is clever enough to spot that there is no load (or infinite resistance), and won't necessarily apply a voltage. If there is a voltage applied, it'd be between one of either two pairs in each connector. So it'd be between 1&2 OR 3&4, and 5&6 OR 7&8.

Last thing - the motor drivers are adjustable with the small screw potentiometer. Turning clockwise turns the power up, so send your lock command, then twizzle each adjustment screw around and see if anything grip happens on the motor. Listen too, there's usually some whining if there's current flowing.

I'm fairly certain that the pin assignments haven't ever changed since the beginning, but tell me what version board you have (it's printed on it somewhere) and I'll double-check the schematics. I guess you are using POLARSHIELD as the MOTHERBOARD in the firmware.

Good work on getting it running too - I recently had to revisit an old machine here, and caught myself out on every single gotcha there is (wrong screen, wrong calibration...)

sn

Any voltage at all on the output pins is a sign that the supply voltage is enough to run the stepper drivers, so that's good. And if you can measure a voltage on the output pins, then that _must_ be enough to interact with the motors in some way. It might not be enough to lock firmly, but it'll be doing something.

When you say output pins, you mean the green sockets that the motor cables plug into, right?

Is there any chance you have got the motors wired up wrong? If there is voltage, there will be some current flow if the motors complete the circuit. If the two coils in the motors are not wired up to the two pairs of wires in the connector (pair a: 1&2, pair b: 3&4), then the circuit isn't complete and nothing will flow.

Try swapping 2&3 maybe.

sn