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Thread: Servo Alarm 401 on Fanuc O-Mate M

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    Default Servo Alarm 401 on Fanuc O-Mate M

    Hi,
    My machine is Bridgeport Interact 316 with Fanuc Series O-Mate M
    I'm getting this alarm on Screen " 401 SERVO ALARM : (VRDY OFF)"
    I press the reset soft key and sometimes it goes off and then comes back on in about 5 mins.
    Any Ideas ?

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    Hallo, 99% your problem are the MCC on power pcb of servodrive axis..replace mcc on power pcb of servo drive axes 1 and 2..

    Bye, ANdrea



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    OK,
    I've attached 3 pics of the 3 axis Servo Amp.
    When I turn on the main power to machine it looks like in the 1st pic. There's a small red LED lit in the top left corner is this supposed to be lit ? This LED stays lit all the time. There's also a green LED lit on the bottom left.
    Then when I turn on the controller (2nd Pic) the DRDY green LED lights and all seems OK.
    After about 3 or 4 mins the DRDY green LED goes off (3rd Pic) and I get the alarm on screen 401.
    I've checked the PCB Voltages +24, +15, -15, and +5 and they are all ok.

    I'm wondering would coolant be leaking into one of the motors on the machine, would there be a cable problem or do I need to get a new servo Amp or the top servo PCB ?

    Attached Thumbnails Attached Thumbnails -main-power-jpg   -controller-initially-jpg   -approx-3-mins-jpg  


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    The top red LED is normal- that indicates the drive is charged. 401 is a pretty generic alarm, and since you aren't getting any of the red leds on (alarm) im guessing not a cable problem. You can remove the motor power leads from the drive and see if the condition changes. I'm pretty sure there is a diagnostic page on the 0 to see whats causing it, but I only have i series manuals on my computer.



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    This may help?
    n = axis.
    Al.

    Attached Thumbnails Attached Thumbnails -alarm4n1-pdf  
    CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).

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


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    As some one pointed out the 401 VRdy Off alarm is pretty generic alarm all it is telling you is the drive is not ready. The actual cause of the alarm may not even be in the servo drive or system and could be something as minor (to the servo system) as the servodrive receiving an external e-stop signal or loosing the enable signal. That you are not getting any alarms on the drive rules out alot of potential sources for VRDY OFF.

    Once you determine that the problem is not external and is in the drive/servo system you can probably rule out cabling or a bad motor (If I understand you properly this is happening without calling for a move and the cables are not being flexed) MCC is a common cause of this kind of problem, a break in the coil wire that will open up as the coil warms up, shutting down MCC. This allows the coil to cool and then MCC will work again until it wrmas up and the cycle repeats. Two ways to check this are 1) apply power to the coil (rest of drive can even be unpowered) and see if it turns off after the 3-5 minutes it normally takes to shut down. Or 2) apply FreezeIt or a similiar product to the coil to get it really cold and see if it takes longer to shut down (or inversely after it shuts down use FreezeIt on it and see if you can use it again faster)

    If MCC is not the problem other likely problems are the input chips on the board, specifically the ones that get the estop/drive enable signals. These are usually on a chip manufactured for fanuc (like an RV05) though some models and revisions used generic chips. If you do not have a set of prints for the circuit board (Very few people do) you'll just have to trace it back from the pins on CN1. The FreezeIt check would be easiest on these.

    Also try removing the top board from the drive. From the pictures it looks like you have the type that does not even scews holing it on just the plastic clips around the outer edge. Then just re-install it (you may want to do this a couple of times) If bad connections between the top board and the rest of the drive are the problem this will usually be enough to clean the connectors.

    Cold solder joints are also a frequent cause of this type of problem. This would be a bad solder connection which overtime gets a thin layer of oxidation in the "crack" as it heats up it can cause the "crack" to loose conductivity. These can be a little more difficult to find the usual method is good lighting, good eyes and a good magnifying glass and knowing what to look for.


    A new servo amp is expensive, even a rebuilt or reconditioned one will be thousands of dollars. Fanuc usually can sell you brand new amps even for old machines but the prices have gone through the roof, I've seen quotes from them for over $20,000 for a dc spindle amp. Having a good tech look at the machine will cost you some money but in the long run it will save you money. Having a bad tech look at it can cost you more. If your shop is not big enough to have it's own maintenance people try to find a good independent contractor tech as they usually cost less then going through a dealer.



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    Hi guys,
    Thanks very much for the replies.
    The problem as you pointed out for me is one of the MCC's. It starts up fine and after a few mins when the machine alarms out the MCC is very hot. I did a freeze test as suggested and it lasted a lot longer. So as you said it's failing when it warms up. So all I need to do is get an MCC or 2 and solder them in and everything is sorted.
    The problem is sourcing the MCC's. They're "Fuji Electric Aux. Relay P/N.: FMC-OASZ42 4a". I can't find them anywhere. I'm going to try and get someone to cross ref. them but if I get a different make I'm sure the mounting will be different and it'll be a bit messy.
    I managed to source a new drive complete with the top card on ebay so that's good I suppose. 1k euro, not bad if it's working ! I expect to see it in a few days. So hopefully the machine will be back up next week. I still want to repair the other drive, put it back in m/c and sell the one I'm getting again or have a spare. If anyone knows anywhere I could source 2 MCC's please let me know.
    Thanks very much for the help everyone, I appreciate it.

    Mark.



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    If all else fails you could always try calling Fanuc and buy the MCC from them.



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    Hi,
    Fanuc UK won't supply the MCC's. They offer to exchange the board that the MCC's are mounted on for 1360.00 GBP.
    The repair guys won't supply them either understandably.



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    Quote Originally Posted by mbpp View Post
    Hi,
    Fanuc UK won't supply the MCC's. They offer to exchange the board that the MCC's are mounted on for 1360.00 GBP.
    The repair guys won't supply them either understandably.
    Since the merge of GE Fanuc with Fanuc, some guy in Luxemburg decided to change the policy regarding spare parts. Several items that were available in the past (We bought ourselves on several occasions those FUJI MCC's from Fanuc) are no longer available. You can still "buy" them if you ask a service intervention, but then you have to pay at least 500 Euro for the intervention.
    In the past, we were very satisfied with the Fanuc service (mostly in contact with Fanuc France), but with this changed policy, it goes a big step BACKWARDS.

    Anyway, on topic again: unfortunately it is not easy to get the FUJI contactors here in Europe, but it is possible to use the OMRON G7J series as an alternative. The pins are a little off as the spacing is a bit different, but with a little bending and the clearance in the PCB holes, you should be able to insert it properly and solder it again on the PCB. Those contactors can be bought for instance at RSComponents and go from 18 to 35 Euro a piece.



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    Default Fanuc OT 401 Alarm

    Hi all,
    I know 401 is a generic alarm but I'm wondering if anyone will be able to help me narrow it down... The x-axis on my Denford cyclone was a bit 'sticky' as when running a program it would occasionally stop moving and then jump all at once. After a few minutes of this it gave up all together and gave me the 401 alarm. The red led is lit on both boards. I have replaced a BUV60 (diode?) on one drive as it appears to be faulty (This was a problem once before) but this did not work... I have taken the motor off the axis and both appear to run freely... Any other ideas guys?

    Thank you,

    Paul



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    Quote Originally Posted by Bakes144 View Post
    Hi all,
    I know 401 is a generic alarm but I'm wondering if anyone will be able to help me narrow it down... The x-axis on my Denford cyclone was a bit 'sticky' as when running a program it would occasionally stop moving and then jump all at once. After a few minutes of this it gave up all together and gave me the 401 alarm. The red led is lit on both boards.

    Any other ideas guys?
    It sounds like a problem indeed with the servo amplifier. But you'll probably have another alarm besides this generic 401 alarm. Investigate that one (HC, HV, ... LEDs on the board), as the 401 is just the consequence of the fault inside the servo amplifier: fault servo amplifier -> turns off unexpectedly -> control notices this and gives alarm 401 (as the drive should be ON/RDY, but it is OFF/NOT RDY).

    "Sticky": it looks like the motor is only fed with 2 or 2,5 out of 3 phases, probably a broken transistor module (but instead of the usual short circuit, one of the 6 legs has an open circuit). Take off the PCB (remove the many screws) and you'll find the modules underneath it.



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