[vfsi]

My situation:

Fanuc 6M-B Control Mori Seiki 45/40 3 Axis Mill
Velocity Control Unit A06b-6047-H003 PCB A20B-0008-0320/08C

Start of problem: Powered up one day and received 401 servo error. Cycled power all was good. A few work days later the 401 servo error returned at power up. A power cycle added errors 411 and 421. Now every power up results in the 401, 411 and 421 errors.

Upon startup:
Bubble Read as it should then when the servos are powered up the 3 MCC relays kick in then after a few seconds they drop out.

Control displays errors
401 serov
411 x-axis
421 y-axis

No errors on the drive LEDs. No errors on the spindle LEDs
Drive Vcc RDY LED is lighted PRDY LED flashes on right before the MCC's drop out.
Hydraulic pump reaches pressure, Lube pump activates.

Incoming voltages 212.6 VAC, 212.6 VAC, 213.1 VAC

Voltages to the drives 101.2 VAC and 175.6, 175.9, 175.9 VAC

Drive voltage 22.78 VDC at CH15, 15.13 at CH16 VDC, -15.11 VDC at CH17

Tables are not on the limits and have not been on the limits recently.

After reading all the post about my issue, the possible causes could be bad MCC(s) or bad main board? How do I test either or both. Is the 3 phase AC voltage into the VCU's correct? I couldn't find any documentation on what it should be.

Any other Ideas?

Thanks for your help.

[yaddatrance]

First check your servo drives for alarm LEDs. Also check your fuses. The other two errors will go away if you fix your 401 error.

[vfsi]

I have tested all the fuses that I can find and they test good. I don't have any alarm LEDs lit on any of the three VCU's nor on the Spindle drive. So I do not know what to check next.

Any other Ideas?

Thanks