I have an old MiniTech Minimill-2. It had its own control with a parallel port interface. I tried communicating with it with an Arduino and GBRL v.9. I could power it up, but could not get any movement out of it. I removed the cover of the control and found someone had been in there working on it before. I decided to scrap the control for the arduino, cnc shield, and A4988 drivers. While assembling everything, I found the existing steppers were 5 wire unipolar 35 oz-in. I messed one up cutting the trace to convert it to 4 wire bipolar. I also found one was shot, so I bought 3 new 4 wire bipolar stepper motors. Since I was tearing it apart this far, I cleaned the whole thing up. I got all guides clean and sliding very good and all acme screws clean and lubed. Surprisingly everything is in really good shape. I assembled everything except for putting the table and the spindle on it. I wanted to make sure there were no issues while I could still see and get to everything. I am supplying 12v via a trolling motor battery to the cnc shield. I plan to use a computer power supply. While wiring the motors, I noticed 2 different layouts. One was a picture of the CNC shield with labels beside the pins. Top to bottom it shows B2, B1, A1, A2. On a schematic for the A4988, it showed top to bottom 2B, 2A, 1A, 1B. Looking at it I thought these were the same where B1 and B2 are the same as 2A and 2B (Top to bottom would be negative and positive of the 1st coil then positive and negative of the 2nd coil). Wiring the motors this way, I got smooth movement out of the Y axis. No movement out of the X axis, but a lot of noise. No movement out of the Z axis and a very faint hum. This is where I thought maybe the 2 different layouts are not the same. Maybe the A4988 requires the 1A, 2A together and 1B, 2B together. This would put the middle 2 pins to the 1st coil and the outside 2 pins to the 2nd coil. I swapped some wires and give it a go. This time I got smooth movement out of the X axis. No movement and a lot of noise out of the Y axis. No movement out of the Z axis and a faint hum. I did find out I could spin the Z by hand and then the motor would spin it. Now I am totally confused. I wired the Y axis back the way it was. Now I got smooth movement out of the X and Y axis. The Z moved, but if you jog in the + direction, it will move up and then the second time you hit the + it will move down. I tried running a program. The X and Y moved good. The Z never moved at all. What is the correct wiring and why are all the motors behaving differently? Thanks in advance.