Hi,

we have a Takisawa Lathe with a Fanuc 6T controller in our shop.
It used to blow one fuse on the Z-Axis driver input from time to time in the past. Always the same leftmost fuse (and the correspnding flag-fuse).
But the machine was used and worked, cause this happend once a month / few times a year.

Now this changed and the fuse is blown immediatly after Power-On (still always the same leftmost fuse).

What I've checked:

- Disconnected the motor-power - lines from the driver-unit: The fuse was not blown. The machine gives an alarm 401 after 1 or 2 seconds.
- Measured the motor-lines: About 0.5Ohm between and 30kOhm to ground.
- Tried to turn the z-axis by hand: It is very easy. No mechnical problem.
- Checked the brushes: They are still OK, but lot of dust in there. Cleaned the brushes and blown some clean air through it.
- After cleaning of the motor, the resistance to ground was about 50kOhm.

My thoughts and assumptions:

- The power-semocinductors / Thyristors in the drive-unit should be OK, otherwise the fuse should also be blown with disconnected motor.
- The motor should also be OK.

Should we try to test the motor with a 12V car battery or is it already proven that the drive-unit is toast?

Any ideas? Thanks a lot!!!