A CNC machining center with FANUC 7M, the CRT shows ALM05 and ALM07 alarm when turn on the power.

ALM05 of FANUC 7M means “CNC in emergency stop”

ALM07 of FANUC 7M means “Servo driver system not ready”

Usually the machine parameters of the CNC controller lost, or servo driver has problem will cause this problem.

Check the machine parameters and they are fine, but the alarm lights of the speed control unit are off, this means the servo driver system not ready, so the problem from the speed control unit.

Check deeper then found the 30A fuse(the thyristor major loop) and 1.3A fuse(the control loop) of the Z axis servo driver were fused, this means the Z axis driver has short circuit.

Normally this should be caused by breakdown the thyristor, measure the thyristors of the major loop, there were two thyristors breakdown, which caused the short circuit of the major loop.

Change the two defected thyristors, the driver resume and the machine back to normal.