Yaskawa error A840. Encoder data error

Hi

I have a cnc which the yaskawa drive gives an error on the Z axis. A840 error. I read the manual and it says encoder data error. I checked the encoder and it works. The machine homes the Z axis but does not go down. The error comes when I tell the axis to go down. I'm not sure wether I should buy a new drive or is it the servo motor not giving enough voltage

What could be the problem?
 
Hi,

Have you managed to solve A840, we are also having A840 error. Machine worked for more than 10 years. Now we have changed servo drive with new exact same, rebuilt moto and replace cable with new connectors and still same error.

Any idea?
 
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