[Philipf]

Hi Phill ,

from your photo I can see the EL817's are used for the direction and enable inputs
R15 & R16 are 1K pull up resistors connected to the TB6560

If you bypass the 6N137 that isolates the step signal
you will need to check the breakout board can sink 10mA as the pullup resistor R14 is 510 ohms

John

What I will try to start is put all ICs back on the board and jumper the EL817s, to check what happens. Then I will jump the 6n137 and see what happens. If still no luck I will run the shop and get a battery for my multimeter

Thanks for the help John