[gusf]

Hi,

Just powered up an old urawa mill with fanuc 6m control, it has been off power for about 4-5 years (i just bought it).

When i first turned on the power and it tries to turn the servos on im hearing a short hum (quite powerful) and it then throws a 401 alarm. when checking the servo cards (A20B-0007-0361) one of them is showing a red light (OVR).

I tried changing two phases on my incoming power and the humming dissapered on startup, i see all servo cards showing a short green signal before all turnes off and i get same 401 servo alarm.

Can anyone guide me here?

Thanks
Gus

[Dan Fritz]

I would pull the fuses on all the drives and try to power up. The larger Fanuc drives have 3 cartridge fuses and 3 1.3 A indicator fuses on the back. Pull all 6 fuses to disable the drive. The smaller drives have just 3 15 A indicator fuses. Pull those 3 fuses to disable those drives.

With the fuses removed, be sure you don't have an axis that will "drift" down when the power is on. Some vertical Z axes use a brake in the Z moter, so if the brake releases with no fuses in the drive, the Z will drift down. Block the Z axis with wood to prevent this.

With the servos disabled, power up the control and try to run the coolant pump. That should tell you if the phase rotation is correct or not. Then, check the voltage at the back of each drive unit. You should have 3-phase AC on terminals "A", "1" and "2". You should see about 120vac for model 10 and 20 motors, 90vac for model 5 motors, and 60vac for the small model "0" motors. Be sure that all three phases are there.

That should get you started.

[yours_prabhat]

The alarm 401 means = alarm on 1st Axis, please check the X axis motor , Mains input power and Feed back Cable , Also check The Fuse, Contactor Contacts, Brake if any present in axis , If everything is Ok, Interchange the X axis drive with Z axis If both are identical , If problem shift in Another axis Than repair the X axis (faulty) drive.[Interchange the drive only when both drives are identical], May be one has power regulator unit and another may not have.
[email protected]

[gusf]

Thanks for your help.

I just checked my fuses and i found that 5 out of 12 (15a) were shot
On the servo cards. What could have happened?

X axis all are fine
Y axis 2 shot
Z axis 1 shot
Atc 2 shot

Thanks
Gus

[yours_prabhat]

please replace the Fuse with the Similar rating and re run the machine, There is no other possibility Except the short circuit or Overload for the Fuse Blown, Whereas It is hard to say That in all 3 axis The Overload or a Short Circuit at a time, So please replace the fuse and run the machine again If problem persists Please communicate with as much as details and photograph on [email protected]
[Fuse Never Shot It blows or Open]

[gusf]

Dan,

Thanks for your reply,

I removed all fuses and still gets the 401 error, i noticed a red diod (FAL) on the "A20B-0008-019" board.

/Gus

I would pull the fuses on all the drives and try to power up. The larger Fanuc drives have 3 cartridge fuses and 3 1.3 A indicator fuses on the back. Pull all 6 fuses to disable the drive. The smaller drives have just 3 15 A indicator fuses. Pull those 3 fuses to disable those drives.

With the fuses removed, be sure you don't have an axis that will "drift" down when the power is on. Some vertical Z axes use a brake in the Z moter, so if the brake releases with no fuses in the drive, the Z will drift down. Block the Z axis with wood to prevent this.

With the servos disabled, power up the control and try to run the coolant pump. That should tell you if the phase rotation is correct or not. Then, check the voltage at the back of each drive unit. You should have 3-phase AC on terminals "A", "1" and "2". You should see about 120vac for model 10 and 20 motors, 90vac for model 5 motors, and 60vac for the small model "0" motors. Be sure that all three phases are there.

That should get you started.

[gusf]

I got my fuses today and im free from the 401 alarm! all axis are moving.

I still have the alarm lamp active (but no alarm codes) and i cant seem to write anything down to memory? when i press input button nothing happens..

im little low on oil and coolant.. dont know if that will activate the alarm?

[gbowne1]

Yeah, there is a low fluid alarm. It depends on how low the level is. I generally never let the sump(s) go dry. Keep it full so there won't be risk of this particular alarm happening.

Looks like you have the "German" operator panel.

I actually miss the old green monochrome CRT.

There are aparently several different versions of the "System 6" CRT/MDI panel.. including the 14" monochrome similar to the System 3 & System 5. They are all numbered A02B-0051, -0052 -0053, etc. Anyone knows what CRT/MDI unit goes with what 6M and 6T model let me know. There are also several different keyboards too.

[gusf]

I filled up all fluids and i still get the alarm, can i see somewhere what it is complaining about?

Yeah it has a german operator panel.. can't understand a thing

version of the fanuc 6m is series 901 vers. 02

Yeah, there is a low fluid alarm. It depends on how low the level is. I generally never let the sump(s) go dry. Keep it full so there won't be risk of this particular alarm happening.

Looks like you have the "German" operator panel.

I actually miss the old green monochrome CRT.

There are aparently several different versions of the "System 6" CRT/MDI panel.. including the 14" monochrome similar to the System 3 & System 5. They are all numbered A02B-0051, -0052 -0053, etc. Anyone knows what CRT/MDI unit goes with what 6M and 6T model let me know. There are also several different keyboards too.

[gbowne1]

Fortunately Google has Google Translate (Google Translate)
so that you can go to and try typing in whatever german phrase you need to know.

I belive the 901 software is pretty recent as far as the System 6 goes.

Look at your DGN page. This should show all of your diagnostics. The 6M-B has a DGNOS key. I believe that the DGN 800's are what you are looking for here. Post a picture of them, if you can get to it.

Seems you have the axes drive board that has a ribbon cable. See Attached pic for the A20B-0007-0361. Your board suggests you might have the A06B-6045-H001 drive(s)

Chances are the manuals for your machine is in German too.

All of the 4xx alarms are all servo related alarms. Which servos do you have?

[gusf]

i have model 5 servos, that issue seems to be solved now!

been reading alot lately and i just realized i've probably made a big mistake, when i first got the 401 alarm i thought that one of the axis was mechanically stuck, since im not able to reach any of the ballscrews by hand (goes inside the machine) i just removed the x and y servos to see if the screws would turn, they did but i surely didn't put it all back in the exact same position. I guess this will cause some problems when i try to zero the machine?

when trying to zero the Y axis it creeps slowly until it gives me a Y axis OT alarm.

Atleast im learning new things....

thanks guys for your help

Fortunately Google has Google Translate (Google Translate)
so that you can go to and try typing in whatever german phrase you need to know.

I belive the 901 software is pretty recent as far as the System 6 goes.

Look at your DGN page. This should show all of your diagnostics. The 6M-B has a DGNOS key. I believe that the DGN 800's are what you are looking for here. Post a picture of them, if you can get to it.

Seems you have the axes drive board that has a ribbon cable. See Attached pic for the A20B-0007-0361. Your board suggests you might have the A06B-6045-H001 drive(s)

Chances are the manuals for your machine is in German too.

All of the 4xx alarms are all servo related alarms. Which servos do you have?

[gusf]

Update.

Ive cleared all alarms, i cleaned my Y axis limit switches and it suddenly works!

Now the only problem is i cant zero my Y axis, the decel dog is hitting the switch and that works, then it just travels into the OT switch.

the right switch is the decel switch and the switch to the left is the OT.

On the X and Z axis i have a physical switch for zero but not for Y


This one is positioned on the Y axis ballscrew, i guess this one is handeling the zeroing for the Y axis am i right? can i in some way see if this one is working?

[gusf]

here is a quote from Dan Fritz from another thread.

1) You jog at least an inch or so away from the home position
2) You turn on the Zero-Return switch and jog towards the home position
3) The axis moves in rapid until it hits the zero return switch (a cam switch)
4) The axis slows down and continues to move until the cam switch drops off again
5) The motor stops when the pulse coder hits the "1-turn per rev." pulse
6) The zero-return light comes on for that axis, and the control "knows" where it is.
7) If software OT limits are used, they become effective as soon as you zero-return.

Notice that you can hit the hardware OT switch if the zero-return (cam) switch sticks in the "on" position. It must turn on, then DROP OFF for the zero return to work.

Also, if the drop-off point of the cam switch is TOO CLOSE to the OT switch, that would mean that the cam switch drops off, but the pulse coder can't make one full turn to fine the "1-pulse per rev." signal before hitting the OT switch.

As you can see on my earlier picture my cam for the OT switch is actually engaging BEFORE the zero return cam drops off...

Can i just adjust my OT cam and try? i have plenty space left on the slide..

[gusf]

i removed the cam that gave me OT alarm, and the Y axis can now zero.

After i realized that this cam also opens my ATC door. So this cam is both giving me the OT alarm and opens my door. This makes me believe that this OT alarm is some kind of safety precaution?? that i need to do something before to override this alarm so i can zero my Y axis..

I just realized im talking to my self :cheers: