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  1. #1
    Join Date
    Oct 2005
    Posts
    7

    Fanuc spindle alarm AL-12

    Something wierd happen me today, A couple weeks ago i had a AL-12 alarm so i dismanteld the spindle servo i measured a bad transistor so today i got my spare parts, so i mounted the new one and started up the lathe, i worked fine. Tested the spindle with 300,500,2000 rpm and i worked fine, So i made a final free spinn test 4000rpm(max), it accelerated up and "boom" the lights i my workshop stared to blink... And then one main fuse for the lathe blew.. so it limped for 2 sec and stopped and i turned it off... I replaced the main fuse and started it up again.. All ok until the spindle servo turns on.. the light starts blink... And i tested to start the spindle and "boom" again.. the F7 fuse blew up(dc link) and again a AL-12 alarm..

    I shall dismantel it again towmorrow.. i saw that a little diod or some thing was burned... A little component with 2legs a "ball 5mm diam." body with a red stripe on one side.. Mounted between the output on the transistor bridge... any one know what it is??


    An why started the lights to blink... i have a tranformator before the lathe.. So is it a short in the driver, and the trafo prevent it from being a "real" shortcut??

    Its a Digital AC Spindle drive, model 12

    //Johan Marquardt

  2. #2
    Join Date
    May 2007
    Posts
    5
    i am no expert but i would check incomming power to the machine
    mechan12

  3. #3
    Join Date
    Dec 2003
    Posts
    24216
    AL-12 in a Fanuc spindle amp, usually means the switching transistors have shorted.
    I found out the hard way, It can be expensive to replace them only to find they blow again soon after, Often the cause is either in the drive board or the drive board has been damaged by the first failure.
    The dead short will be reflected back through the transformer, this is why the lights dim.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
    Join Date
    Feb 2007
    Posts
    38
    I stand behind Al's statement. I've repaired quite a few of AL-12's in my years (over 100). It is standard procedure: Find the defective transistor inside the drive and then find the defective phase on the firing pcb. Either replace the whole pcb (expensive) or replace the the phase associated with the defective T-mod (transistor, diode, photo coupler and hybrid this requires soldering).

    On a side note, that is a diode you are describing in your first post. Keep in mind it matters on how you hook the diode back up to the transistor.

  5. #5
    Join Date
    Oct 2005
    Posts
    7
    I suspected that the light blinking was a short cut in the t-mod and the trafo in the middle didnt make it a full shortcut.

    I will dismantle the driver tonight and do it the hard way, find the bad t-mod and find the bad phase and replace all components in the chain as "not an expert" said.

    Do anyone have any spec. on the diode i mentioned? i didnt find any text on the one thats not broken.

    Is there any more info about the drivers beside the Digital ac servor drive manual. i already has that one. The manual doesnt have any internal conection on the small diodes.

    Best regards johan

  6. #6
    Join Date
    Oct 2005
    Posts
    7
    I dismantled the driver tonight and found that a transistor is bad, but not the same as last time.. this messed things up a little bit... im confused... i also found that a small transistor on the pcb i broken, its the one that controls the big transistor thats broken...

    What to do, of course new big transistor, and the control components for that one... but what about the one that was bad the last time... new control components for that on also, or not.. its not broken now....

    Anyone?? i cant decide...

    Is there any risk that some more stuff has broken because of the "half" short cut the driver made... x,z servo controller?? The nc controller says "1" in the display so it ok.. I cant test any axes with the spindle driver uninstalled.. I cant reset the EMG, beacuse of the spindle error message..

    Best regards Johan

  7. #7
    Join Date
    Feb 2007
    Posts
    38
    If there is now another transistor shorted that is not the same as the first I would recommend replacing the top pcb (firing pcb as we call it) on the drive.

    I would still be careful as where to hook up the diode as it can also damage the board you put on. Without knowing the drive part number it sounds like the diode that goes across the phases for the regen circuit (spindle brake). If there is a local fanuc shop see if they can check the schematics of the drive and let you know which way to mount the anode and cathode side of the diode.

  8. #8
    Just like that changing the components is not Quite sufficient, You have to check the Control Board firing Circuits with Ossciloscope for any mis behaviour. and also check the Motor & Cables any Short Circuit.
    Pl. send the Drive to Service station to Rectify otherwise you willbe wasting Time & Money Because the Transistor Modules are very costlier.

  9. #9
    Join Date
    May 2008
    Posts
    84

    al-12 fanuc spindle alarm

    I have an AL-12 spindle alarm. My drive has only 1 transistor module. How do I determine the driver phase circuit on the top board? I see 7 drivers.
    clay

    Quote Originally Posted by not an expert View Post
    I stand behind Al's statement. I've repaired quite a few of AL-12's in my years (over 100). It is standard procedure: Find the defective transistor inside the drive and then find the defective phase on the firing pcb. Either replace the whole pcb (expensive) or replace the the phase associated with the defective T-mod (transistor, diode, photo coupler and hybrid this requires soldering).

    On a side note, that is a diode you are describing in your first post. Keep in mind it matters on how you hook the diode back up to the transistor.

  10. #10
    Join Date
    Feb 2011
    Posts
    640
    a buddy that does a lot of repairs suggested that he ALWAYS replaces ALL the optocouplers before firing up with a new output transistor. the switching transistors can be checked, but he said he had a couple warranty issues that could only have went back to the optos- so he always replaces them now, never had another issue...

  11. #11
    Join Date
    Dec 2008
    Posts
    239
    Check the Transistor Module , The input voltage circuit up to module , The capacitor discharge Circuits , The Opto-couplers, The small Diodes , and Driver Switching IC .
    Just cross examine the Regenerative Circuit and 5 V circuit for a concrete solution.
    regards

  12. #12
    Join Date
    May 2008
    Posts
    84

    al-12 alarm

    There are 7 optocouplers / phase drivers, on the to pcb...but only ONE power transistor module. I have a scope. Is there a way to determine which opto/phase is bad? The book shows some normal/abnormal waveforms. But the book does NOT match the machine/control. The book shows a different power (dual) transistor module, and the Top PCB is very different, with different fuses, etc..

    My understanding from the book & other posts, is the power transistor doesn't switch on until you command a spindle speed. IOW, you test the circuit by commanding an M3/M4 Spindle speed zero. Then check waveforms & voltages.

    Quote Originally Posted by tc429 View Post
    a buddy that does a lot of repairs suggested that he ALWAYS replaces ALL the optocouplers before firing up with a new output transistor. the switching transistors can be checked, but he said he had a couple warranty issues that could only have went back to the optos- so he always replaces them now, never had another issue...

  13. #13
    Join Date
    Oct 2013
    Posts
    1
    Can a shorted spindle motor cause the AL-12 ? I would think that if the armature is shorted excessive current could flow
    thru the amp damaging it or does the amp limit the current output to protect itself ?

  14. #14
    Join Date
    Dec 2003
    Posts
    24216
    You can soon tell if it is just the motor, disconnect it and see if the alarm appears.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  15. #15
    Join Date
    Feb 2010
    Posts
    31

    Re: Fanuc spindle alarm AL-12

    First off I want to thank all you guys for your posts here concerning AL-12 alarm on spindle drive unit....

    I have a Kitamura Mycenter-1 that has a Fanuc OM control....the other day, I had the spindle stop working and I got the AL-12 alarm.

    I tried to avoid messing with the Board itself......so I just replaced the main transistor inside of the unit......

    When I first put power to machine....I could home the machine....but when I tried to activate spindle...nothing....no alarm either.
    When I shut down....the drive readout went from "0000" to "AL-10 low voltage" for only a split second at shutdown....I turned it on and off like 3 more times and the spindle finally came back on. I ran the spindle for about 5 minutes....even changed a tool.....sent a program, went to run it.....got the AL-12 alarm again.....

    So, I know what I "didn't do" and that was change out the parts on the board that were described by "not an expert" here on this thread.....and that is to change out these parts below on the board.....

    1.) Transistor (in my case it is a "ET191"...quantity 7)
    2.) Diode for transistor (self explanatory...quantity 7)
    3.) Photo coupler (mine is a "TLP550"....quantity 7)
    4.) Hybrid (still trying to figure out where that is) - NEED HELP ON THIS ONE!!!

    A.) Main Transistor obviously needs replaced again....it is "A50L-0001-0125#A"...no problem there.

    below is a pix of my board and of the transistor that was pulled from the unit the first time.

    Im really looking for reassurance that I am not missing anything here in the board repair......should I replace all capacitors?......again....help with the Hybrid please

    Here is a pix of the Board....
    A16B-1100-0200 /12A



    Here's a pix of the transistor unit


    Any help would be awesome!!!!...thanks!

  16. #16
    Join Date
    Aug 2007
    Posts
    793

    Re: Fanuc spindle alarm AL-12

    why are sure that namely PCB is faulty? have you checked motor by megatester?

  17. #17
    Join Date
    May 2008
    Posts
    84

    Re: Fanuc spindle alarm AL-12

    Quote Originally Posted by metalmover View Post
    First off I want to thank all you guys for your posts here concerning AL-12 alarm on spindle drive unit....

    I have a Kitamura Mycenter-1 that has a Fanuc OM control....the other day, I had the spindle stop working and I got the AL-12 alarm.

    I tried to avoid messing with the Board itself......so I just replaced the main transistor inside of the unit......

    When I first put power to machine....I could home the machine....but when I tried to activate spindle...nothing....no alarm either.
    When I shut down....the drive readout went from "0000" to "AL-10 low voltage" for only a split second at shutdown....I turned it on and off like 3 more times and the spindle finally came back on. I ran the spindle for about 5 minutes....even changed a tool.....sent a program, went to run it.....got the AL-12 alarm again.....

    So, I know what I "didn't do" and that was change out the parts on the board that were described by "not an expert" here on this thread.....and that is to change out these parts below on the board.....

    1.) Transistor (in my case it is a "ET191"...quantity 7)
    2.) Diode for transistor (self explanatory...quantity 7)
    3.) Photo coupler (mine is a "TLP550"....quantity 7)
    4.) Hybrid (still trying to figure out where that is) - NEED HELP ON THIS ONE!!!

    A.) Main Transistor obviously needs replaced again....it is "A50L-0001-0125#A"...no problem there.

    below is a pix of my board and of the transistor that was pulled from the unit the first time.

    Im really looking for reassurance that I am not missing anything here in the board repair......should I replace all capacitors?......again....help with the Hybrid please

    Here is a pix of the Board....
    A16B-1100-0200 /12A



    Here's a pix of the transistor unit


    Any help would be awesome!!!!...thanks!
    I sent my drive to Radwell/PLC center for repair. plcCenter.com. Total cost was $916 with a 2 year warrranty. I paid extra for a 48hr expedite. ($183)

    Alternately you will need to replace:
    1.) Transistor (in my case it is a "ET191"...quantity 7)
    2.) Diode for transistor (self explanatory...quantity 7)
    3.) Photo coupler (mine is a "TLP550"....quantity 7) These are usually the culprit, from my research.

    Opinion. The hybrid is most likely not bad.
    I would consider the cost of replacing the TM again. The above components will not be expensive.
    My drive failed due to overheating from a failed cabinet fan, and a little later on, ultimately a failed motor mounted fan that took out the motor tachometer. The motor was fine.

  18. #18
    Join Date
    May 2008
    Posts
    84

    Re: Fanuc spindle alarm AL-12

    I would also replace all the Electrolytic caps in the motor drive circuit. Even if they are not bad now, they will go bad soon.

  19. #19
    Join Date
    Feb 2010
    Posts
    31

    Re: Fanuc spindle alarm AL-12

    Okay guys....Im still in the middle of this repair....Have a "Diode" question......

    First I bought the book for the drive unit.....my particular unit is called a "3s" (A06B-6059-H003)

    Bought the transistor module (this time I got 5 of them )
    Bought the Transistor (in my case it is a "ET191"...quantity 7)
    Bought the Photo coupler (mine is a "TLP550"....quantity 7)


    The Diodes....
    Best I can tell from the book is that my diodes I need are these numbers below....
    A50L-2001-0103 / 12JH11
    A50L-2001-0103 / 12JG11

    one in my hand reads BB100494? (best I can tell...the last 2 digits "94" are smaller than the BB1004)

    I cannot find these anywhere......is there an equivalent that you guys may know about....or someplace that doesn't want an arm and a leg for them?????

    I really want to do this repair in total.....the shop next door has a guy who works on circuit boards, so Im blessed there.....just need the last parts......

    Thanks again guys......and Ill take pix of everything as I do it

  20. #20
    Join Date
    Feb 2010
    Posts
    31

    Re: Fanuc spindle alarm AL-12

    Hey guys..still wondering if you guys could answer my Diode question....the diodes on the board that need to be replaced....anybody know about em???

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