SRVO-68 DTERR Grp :1 Ax: 5 & Ax: 6

  • We are getting intermittent DTERR faults on axis 5 and 6 of our M710iC. We have changed the cables going from the base of the robot to the controller , from the base of the robot all the way to the pulse coders. Replaced pulse coder on axis 5. Recording axis positional data on every fault condition and cannot seem to see a trend. Looking for some ideas as to what we might be missing. Could this be a servo motor heating up too much? Any suggestions would be welcome.

  • AD
  • On older robots, replace the SIF module and/or the DSM module, but I think they are not used anymore on modern robots. (I am not sure, we only have old robots)


    Very important ! Check the grounding on all cables and between the robot and controllercabinet.

    It is a mayor cause of all sorts of faults.


    Check not only the cables, but also the pins in the connectors if they are still locked and can't be pushed in.

    Check if the pins and bushes still look good.


    Take a good look at the coupling between the encoder and the motor, and check if it is not broken.

    This one kept me once searching for more than a week....

  • Thank you, Checked all the grounding points and they seemed good and tight. coupling between the encoder and the motors are fine. The odd part is its happening on 5 and 6, which would make me believe that it is something common to them both. Does the servo amp handle the signal from the encoder or does that go somewhere else?

  • 1) when you replaced the cable, did you also replace the connectors too? Are you sure both the encoder connector AND the amplifier connector (CRF8) are new?
    2) Do you have a spare motor to swap in place of axis motor 5 for example?
    3) does the fault occur on certain positions/postures?


    This is strictly a communication fault between the encoder and the amplifier, amplifier requests encoder data but encoder returns nothing, its either a bad connector (encoder pin connector or CRF8 connector), a faulty, maimed, scratched or not properly shielded cable, a loose ground or lastly a bad encoder.

  • 1) when you replaced the cable, did you also replace the connectors too? Are you sure both the encoder connector AND the amplifier connector (CRF8) are new?
    2) Do you have a spare motor to swap in place of axis motor 5 for example?
    3) does the fault occur on certain positions/postures?


    This is strictly a communication fault between the encoder and the amplifier, amplifier requests encoder data but encoder returns nothing, its either a bad connector (encoder pin connector or CRF8 connector), a faulty, maimed, scratched or not properly shielded cable, a loose ground or lastly a bad encoder.

    Thank you for your response.

    1) Cable came with new connectors already terminated.

    2) we have a spare motor, we have just changed the axis 5 encoder so far. but not the motor

    3) we have been monitoring the joint angle at fault, the only joint that comes close to being in the same area is joint three anywhere from -55 to -20 on the joint position.


    It always seems to happen on jt 5 and 6 at the same time. could a bad encoder on 6 be causing the fault on 5 and 6? If the cables and plugs are all new and the encoder on 5 is new.

  • When you remove the topboard, check the soldering of the CRF8 connector.

    Use a microscope or a strong magnifying glass and look for bad joints and cracks in the soldering.


    Watch out, the servo has strong capacitors, be sure they are flat before handling the servo.

    They can give you a very shocking experience...

  • The A06B-6240-H106 is a single axis servo drive, most used for an extra axis.

    The servodrive mentioned in the manual is the six axis drive with the topboard A20B-8101-080.

    OK thats what I thought, We changed out the correct servo amplifier. No change. The only thing that has yet to be changed is one of the pulsecoders. everyhting else from the servo amp to axis 5 & 6 has been changed.

  • This is strictly a communication fault between the encoder and the amplifier, amplifier requests encoder data but encoder returns nothing,

    Famous_Fella makes it simple with this statement above - amplifier, Pulsecoders, or cables in-between.

    Changing the amp did not fix.

    New Pulsecoder on J5 did not fix.

    This leaves the 2 cables in-between.

    The RP1 cable goes between the amplifier CRF8 and the robot RP1 connector.

    The robot internal harness should be a continuous cable from the RP1 connector to each Pulsecoder.

    The one thing that J5 & J6 Pulsecoders share is their power connections at RP1-19 (5V) and RP1-40 (0V).

  • Thank you for your response.

    Apparently all this has been replaced, servo amp right to each pulse encoder.

    Only down side is some of this work has been carried out by other shifts, so I do not know the quality of their work or even if what they say they changed is in fact what they changed.

    Sadly I am not in charge of this issue so my hands are tied. I have passed on all this information you have been kind enough to share with me.

    When a resolution is found I will report back incase anyone is curious.

  • I permanently fixed this issue once by tightening the cable clamp where the cables all enter the robot cabinet. This is a grounding spot, at least in the older Rj2's.

    This was doing the same intermittent DTERR alarm. After tightening that clamp the alarms went away and never returned.

  • Believe it or not, changed the main CPU board and the problem went away.

  • Great !

    Could it be a softwareproblem ?

    I have a hard time believing it is the hardware as there is no physical connection with the encoders…as far as i know…

    I think it might have been software. But I dont know for sure. The CPU board change was at the suggestion of the Fanuc rep but I was not on shift to converse with him as to why.

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