I recently got hold of an old flat bed lathe with Fanuc 6T control. Previous owner had crashed the Z-axis while jogging and didn't touch the machine again, until I picked it up. Swapped it for a couple of hours of labour I did for him.
I hooked it up at home, but keep having the 401 alarm message. When I fire up the machine with the main switch, hydraulics and fans come in immediately. When I power up the NC, the PRDY signal on the X-axis comes in shorlty and the MCC of X-axis is pulled in. Z-axis gets no PRDY signal. After 1 second or less, the PRDY signal of X-axis drops and alarm is on.
I already checked the following things:
* 24V on Velocity Control PCB's: OK
* +15V and -15V on that board's: OK
* Thermo OL switch on Z servomotor was in open condition when I checked. After taking that from motor, the switch went to closed (is NC I believe) and still is.
* All aux contacts on both MCC of VC are OK. (NC and NO contacts).
* Checked diagnostics, but don't seem to have diagnostic 707. jumps from 702 to 710...
* All limit switches are 1 (NC) in diagnostics, so that seems to be OK.
* Checked cable from master PCB to both VC units, all leads are OK
So it seems the NC is the problem here. According to the maintenance manual, I should replace the master PCB with such an error, but maybe somebody hs a better idea?
Check the signals VRDY X,Y,Z on the side from drive of axises. I put the scheme with these relay contacts from drive. Any signal can be a reason of the error 401.
I get a short VRDY signal from X-axis, but never a VRDY from Z. Doesn't the Velocity Control needs the prdy signal first to get the MCC pulled in? At least this is what happens to the X-Velocity Control and that seems to work, however very shortly.
When the Numeric control cuts off the PRDY signal, the VRDY drops.
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Fanuc 6T no PRDY on Z- controller
