Weak Motor

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    I have the 4 Axis Pro board and the A axis motor seems to be weak. The problem is that the motor turns very jittery. I can also stop the motor just by pinching the shaft with 2 fingers. It is acting like it is under powered.

    I confirmed it is not the motor by swapping the motors on the Y and A axis. I also confirmed that it isn’t the parallel port by switching the A axis to different pins on the port. I also confirmed that the amps were set the same on all four motors.

    Does anyone have a clue what is wrong with it? Is it a blown driver chip?



    Troubleshooting is always slower than you’d like (see blog post The Art of Remote Troubleshooting), but here are my thoughts. To speed things up, please answer all of the questions. I don’t mean to sound rude, but I very rarely get the answers, leaving me unable to help any further.

    1. Has the system been working and this is a new problem or is this the first run of the board?
    2. Describe your power supply (voltage and current, brand and model)
    3. Confirm/Insert jumpers in J4 of all axis (disable power reduction feature)
    4. Confirm microstepping jumpers installed (perhaps remove and re-install)
    5. Remove the parallel port cable at the board
      1. Power-up the board
      2. What is the voltage at TB6 – test this at the PC board end, NOT the power supply end)
      3. Measure the voltages at all 4 axis test-points
        (put the black lead of the voltmeter on the minus (-) of TB6)
      4. Do all the motors lock (can’t turn them by hand)?
    6. Reflow the solder joints at all of the blue connectors.
    7. Double-check the wiring to the stepper motors
      1. Re-check all the terminal block screws – make sure everything is still tight
      2. Wire gauge & length to the motors (MUST be stranded wire, not solid)
      3. Are there any joints/connections in the extension cable? Are all joints twisted, soldered and covered with shrink tubing? No crimp-butt joints, no wire nuts, no ‘twist and tape’.
      4. no kinks or damage to wiring between board and motors
    8. Driver chips properly heat-sinked with heatsink compound and cooled by a fan




    Thanks for getting back to me Brian. I was able to fix it last night. The board had been working and this was a new problem. The only thing I did was move it to a new enclosure. So I figured that I must have knocked something loose. I re-flowed all of the solder joints for the a-axis and it started working again.

    I understand about all the questions. I have to debug stuff at work all the time with little or no info.


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