Hello, I have a Okuma LR15-M/3T machine with 5000L-G control. I got it from an auction, so I dont know the history. Machine starts up ok, but the spindle will not move. Sometimes it is working ok, but all of a suddon the spindle does not response. It can be during cut or sometinems just even afte a start up. There is no alarm. Is is a VAC spindle drive. It has two rows of LEDs on the circuit board. When it becomes non responsible, only the first (power on) and last LED (EMS) are lit. It is the same condition as if you push the emergency butten. Somehow the drive stays in the "emergency" state. I have a spare circuit board with the description "VAC Board B". I dont know if they are interexchangable. Could someone please help?

Thank you in advance