Fanuc 401 servo alarm

[sbp]

Hi there;
We have a Fanuc 6M machine which is faulty now.
We get the alarm "401 servo" message .
Please let me know how to overcom this problem.I have checked all the cables and connectors ans fuses on the system.
The 2 green LEDs on the T axis board (on the back of the machine) are OFF all the times.The 18 VAC is OK on T board.
The relay beneath the board will not be active in any case while the relays for X and Y axis are activated for a moment before alarm.(Is this a any sign that how to track the problem?)
Any hint or clue is highly appreciated.
Best regards
SBP

[trubleshtr]

Are there any fault codes appearing on the power supply or amplipher? that may give you more detail,
else, I have had limit switches stuck or jammed with chips causing the alarm to come on.
I think you can (if you have the manual) look up in the parameters the fault down to the bit level, which will also tell you if it is an over-voltage,current ect type of alarm. I have seen over-current alarms with dull tools on the z-axis...

hopefully "Al the Man" will spot this post and help you out as he is well versed in the fanuc systems.

[Al_The_Man]

I don't have my 6M book here at the moment but IIRC 401 is a servo amp fault or no input power to the amplifier, check the fusing and the ac voltage input, What is the type number of the amplifier, as there were several fitted to the 6.
What is the T axis? Is this a turret? Also check the contactor overload reset on the drive if it is a separate drive.
Al.

[EDM_Fixer]

pull the brushes.. blow out the commutator.. look in there is it black ..burnt ..? .. u can polish and clean the commutator w/pencil eraser .. not ink or die eraser they have metal particles and will short it out .. also pull the end cap on the motor ... careful soldered wires !!!! clean the glass scale w/alcahol and a Q tip .. Jim

[khallass]

Hi All:
I just put in a Urawa with the 6M. I am looking for a person to set it up and get it running. It has been leveled and wired. When I fire it up is gives an alarm code 401. It apears to be at the x axis hard stop. I am in Torrance CA 310-326-4111

[rmanning]

HI to all. i'am new here. I also have a 401 alarm on a mori seiki mill mv-35/40 ser#287. It can run for days or weeks and it will not show up. and then bam there it is the 401. It will come on running or just standing still. can any one help me out? thanks rmanning

[To-old for this]

Hello All
I have a Mori SL-7 B with a Fanuc 6 TB 1981 control.
I have been keeping this machine alive for over 20 years.
It has throne me for many loops in the past but this time I am stumped.
It comes up with a 401 servo when turned on. The power supply and all voltages check out. PRDY LED's on the volisaty controle units light for 3 seconds then go out. There are no other indacations. DIGN 707 bit 4 has a 1 = VRDY not ready. any Ideas?

[CNCZILLA]

Hello, i think if i remember correctly the VRDY alarm may indicate the 300v for your buss voltage to the drive is not right. This will be the large shinny bars that connect the drives together usually across the top of the drive. When the machine is powered up check for this 300 volts at your buss bars, if this is not present start tracing back. Probably power supply. Of coarse it is always faster and easier to swap the drives if you have another drive on this machine. For purposes of testing you can swap a lower rated drive just to see if the alarm occurs, you are only testing not running.