Fault Finding On Fanuc Alpha Servo Drives

Fault Finding on Fanuc Alpha Servo Amplifiers This information refers to the 6079/6080/6096 range of Fanuc Servo Drives A drive status alarm appears on the 7 segment display “-” refers to drive not ready (Waiting for an Emergency Stop signal to power up) “0” refers to drive powered up and OK Any other number or letter on this status display is an alarm A common fault is reporting an “8” alarm when the alarm is an “8.” ignoring or adding the full stop An “8” and an “8.” are different alarms (see below) This is also true for alarms “6” “6.”, “9” “9.” and “A” “A.”
Is the drive faulty? A List of Fanuc error codes can be found further down this blog

Fanuc Alpha Servo Drive Repair
Switch S1 and S2 setting on a Fanuc Alpha Servo Drive. A06B-6079-H106

1 – Check the link (6079 drives only) A 6079 drive can give a fault if the S1 Link is in the wrong position S1 – JV Connections (Type A Interface) S2 – JS Connections (Type B Interface) An incorrect setting will cause an Alarm “8”

2 – Check the wiring is correct, L motor is wired in the lower terminals; M motor is wired in the upper terminals, both as U/V/W/E. JV1B connected from the L command plug of the axis card, JV2B from the M command plug. JX1A connected from previous drive, JX1B connected to the next drive in the line. The last drive in the line has a terminator in JX1B. 24v/0v/ESP connected into CX1A from the previous drive, out of CX1B to the next drive in the line.

3 – Disconnect Fanuc motor cable, Meggar the motor

4 – Power machine on whilst in emergency stop. The drive is faulty if an alarm occurs, expect “-” to be the norm.

5 – Release Emergency Stop and power the machine up If alarm occurs, power the machine off Remove motor wires U/V/W/E (Note – this is dangerous on a vertical axis, brake release, slide drops etc) Release Emergency Stop and power the machine up the drive is faulty if alarm occurs, expect “0”

6 – An additional test can be performed for equally sized 6079/6080 amplifiers H201 SVM2-12/12, H301 SVM2-12/12/12, H203 SVM2-20/20, H302 SVM3-12/12/20 (L&M), H206 SVM2-40/40, H303 SVM3-12/20/20 (M&N), H208 SVM2-80/80, H304 SVM3-20/20/20 (L/M&N). The suspect axis can be run from the other amplifier in the drive ie X drives M amplifier, Y drives L amplifier To do this swap round a – X & Y Motor cables U/V/W/E (at the drive) and b – X & Y Command cables (at the drive) (6096 requires parameters changing to swap X & Y round) The drive is faulty if the alarm remains the same as before the test, For example, Alarm “8” is reported on an A06B-6079-H201 drive using JV connections Steps 1~5 above, have been performed and still alarm “8” Remove the motor wires from the lower terminals and reconnect into the upper terminals, upper into lower. Remove JV1B and insert into JV2B, JV2B into JV1B. Retest the machine the drive is faulty if the same alarm occurs, ie alarm “8”. The fault lies elsewhere on the machine if another alarm occurs, ie alarm “9” In this example the drive has detected an overcurrent from the L axis, alarm “8” Swapping the cables over allowed a different amplifier to control the axis. An “8” alarm would remain if the same drive circuitry detected the overcurrent. A “9” would occur if the overcurrent was detected using the other drive circuitry in the amplifier and the fault would be caused externally from the drive. Need Fanuc Spares

fanuc servo amplifier

Alarm Code Fault Remedy
Not Ready Drive is Good
0 Control Ready Drive is Good
1 Internal Fan Stopped Replace/Repair Servo Drive
2 Low control power voltage alarm (LV) Replace/Repair Servo Drive
3 Low DC link voltage alarm (LVDC) Check Alpha Power Supply for Alarm
4 Regenerative dis-charge control circuit failure alarm (DCSW) Replace/Repair Servo Drive
5 Over-regenerative discharge alarm (DCOH) Replace/Repair Servo Drive
6 L-and M-axis over-current alarm (HCLM) Servo Drive or Motor Fault
6. Dot L-and M-axis IPM alarm (IPMLM) Replace/Repair Servo Drive
7 Dynamic brake circuit failure alarm (DBRLY) Replace/Repair Servo Drive
8 L-axis over-current alarm (HCL) Servo Drive or Motor Fault
8. Dot L-axis IPM alarm (IPML) Replace/Repair Servo Drive
9 M-axis over-current alarm (HCM) Servo Drive or Motor Fault
9. Dot M-axis IPM alarm (IPMM) Replace/Repair Servo Drive
A N-axis over-current alarm (HCN) Servo Drive or Motor Fault
A. Dot N-axis IPM alarm (IPMN) Replace/Repair Servo Drive



Fault Codes On Fanuc Alpha Servo Amplifiers

20 thoughts

    SVM SPM AND PSM display NOT READY ( – ) ( – )

    Attached drawing

    With all of the tests that I did.
    * MCON signal is received
    * MCOFF comes to PSM
    * ESP signal right
    Cables is checked –OK

    When I connect the MCON * TO DRDY * all axes (XYZ)
    (Connectors M184 M187 M194)
    The alarm has disappeared, and control come on without an alarm !( PSM NOT COME ON)

    The question :
    what more needs The PSM to work ? (I replaced PSM, without change)
    How to check the PSM without connect to SVM and SPM ?
    Could there be another reason to ALARM 401 VRDY OFF ? Relation to testing, I have already did


    1. Hi
      There are new tests:
      I made a dummy connector, IALM — 0V, * MCOFF — 0V pin5—-pin6 pin7—-pin8.
      Only, when I plug it in, to JX1B in SVM, and I bypass the SPM, (I plug the cable from the SVM JX1-A TO PSM JX1B ) The PSM turn on !!
      The problem in SPM !
      The SPM does not pass the IALM signal to PSM))
      Is the SPM is not good ?( no alarm only not ready (–) )
      Is there any other reason ?


  2. Ai sp-11 it has double digits, the rest of the drives all have a (-) but the one is blinking. The machine doesnt even start up either.


  3. Found out that the model is an Fanuc Alpha A06B-6141-H011, the control breaker was fried. I replaced it now it has a alarm code 24 on the driver.


  4. Hello I have an 01 alarm on my fanuc A06B-6077-H111 PSM the fan is working properly and machine has been cleaned as far as dust. All electrical connections appear tight. What else could I check to determine if the drive is bad and in need of repair or replacement?



      1. I understand It is not a fan problem. I am asking if there is anyway I can test the drive in order to determine it is bad other than the 01 alarm.



      2. If you have the 01 Alarm on your Power Supply, It is your power supply that is at fault, The only way you could confirm would be to swap it for another power supply and see if that runs ok.


  5. Hello.
    Fanuc a06b-6096-h206 we have alarm “b” on the display.
    We have checked all manuals etc. No answer….
    You have an idea about alarm “b” ?


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