[clintw]

we have a 3ne-300 with a dc spindle drive that no matter what rpm you enter it goes to what looks like full rpm. replaced the signal arrival card on the front of the drive with no results. checked the thyristors and they seemed to be fine. then disconnected the cn1 and cn2 cables going into the drive thinking I was isolating the drive from the control. then closed the contactor putting power to the thyristors and the spindle motor didn't turn on so im guessing none of them are open. also m04 does turn the spindle in reverse any help would be much appreciated like how is the drive being told what speed to turn at?

[Kevin77]

Its quite possible that the problem isn't in the drive, but on the Fanuc main board, where that speed signal comes from. Is a GN6 the same as a 6A or 6B?

[tmbruno28]

Hi, please just confirm me you have a fanuc PMC and not a micon8 on your machine

[Leblondmakino]

Hi, If it has a Micon 8 instead of a Fanuc PC board then that is putting out the analogue speed command to the drive..you may have a faulty tacho on the motor..the drive is looking for tach feedback and will keep speeding up the motor as without feedback it thinks the motor stationary..might be the tach brushes that need replacing maybe..

John

[clintw]

from a manual I found on the drive its getting told to go full rpm. so that leads me back to the main control board as you stated, the part number on the main board is a20b-007-0010/06c and is made by fanuc . what would be the symptoms of a bad A-rv03 6161 chip? one of them is discolored and from what I read it takes the pulses coming from the encoder and turns them into a variable voltage?

[Leblondmakino]

I'm not sure if the main board is controlling the spindle motor speed..on my Lathe with 6T it's the Micon 8 PC that does that..the motherboard only deals with encoder feedback so if your spindle motor has a tacho that will not go back to he motherboard but if it's using an encoder it will..if so you could check the encoder cable.

Encoder phases can be checked on the diagnostics and also if you power up the machine in power stop mode and turn the encoder you can see it counting on the 8000 diagnostics if it is ok.

John