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Miyano / Fanuc 6TC - Power up / Losing Power


Oct 19, 2022
Pennsylvania, USA
Just some background, I'm completely new to the CNC repair world, but I'm learning. Thank you for your time in advance!
The company I work for has an old Miyano FNC 200 from 1982. It's a solid machine and has served them well.
It has a Fanuc 6T Model C control and Fuji DSR Spindle drive.

Initially the problem they were having was that during normal turning production the spindle would just stop turning, it would free wheel to a stop no alarms or anything. Mostly this would seem to happen when the spindle was changing speeds, stopping or starting. To get back running, the operator would have to re-power the machine.

Also sometimes it would stop all motion on all axis during a cutting move. It resembled pressing an e-stop. The operator was usually able to reset without shutting down the power.

At that time the spindle drive would show an OCL led illuminated.

-------------This is it's current state-----------

As I went to start troubleshooting this problem, now the machine won't fully boot up. When the main switch is turned and the NC start button pressed, the hydraulics would normally start up, not doing that now. The CRT screen boots up but reads "not ready" at the bottom of most screens.
Showing an 88L LED illuminated. This references the motor cooling fan, I don't see why this would prevent the power to the hydraulics.

I checked for power in the following places
The cooling fans all run
The large contactor beside the main switch isn't pulling, I have power going in but not out.
The input unit (circled in red) has normal ~200V, fuses good.
The master PCB - has good +24 +15 -15 +5 Volts
All 4 servo drives have good +24 +15 -15 Volts

Any idea where to turn from here is greatly appreciated!!
I do have the Fanuc Maintenance manual and an old photocopied manual for the Fuji drive.


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Jan 5, 2014
Vancouver, WA. USA
If the spindle drive is included in the e-stop circuit (it very likely is) and the alarm on the spindle drive causes the e-stop circuit to stay open, you will not get past the “NOT READY” state. If you identify from your wiring diagram which connections on the drive are the e-stop circuit and jumper them out, you should then be able to power up the control. You will still have spindle issues that need to be fixed though.