I'm looking at the SLA7078MRP data sheet and have the 3-axis controller board upside down on the bench. You guessed it, I'm troubleshooting and have been digging back into the design and app notes. The Z axis driver is working fine. (Mach4 via a smartBob). But I have two non-functional channels.
With an ohmmeter, I find about 0.15 ohms from pins 5 or 19 to ground on two of the SLA7078s, but the 3rd chip is open on those two pins, so somehow I must have burnt out the current sensing resistors. Will replace that chip, Y axis.
That leaves the X axis, also not working, but the current sensing resistors seem to be okay. It worked for a while then stopped. The voltages on the SLA7078 pins all seem to be okay, including 0.14V on the reference pin, and it is receiving clock and direction signals. Continuity seems good. But no action from the motor which itself works fine on the z axis. Suggestions for further troubleshooting? Replace?