HEIDENHAIN iTNC 530 Service Manual page 227

Functional control Ensure that:
If this is not the case.
May 2006
The green LED in the area of bus connector X1/X2 is on.
Measure whether the 24 V supply voltage on X9/X10 is available.
Note
If LED is not lit up, despite available power supply, the PL board is probably defective.
Measure all other power supply connections.
Note
On older PLC expansion boards PL 4xx B, you may still find fine-wire fuses (glass fuses) on
the board. These may be replaced, if necessary:
On newer PL 4xx B, the glass fuse has been replaced by an SMD fuse.
The SMD fuse has been soldered onto the board. Contact your HEIDENHAIN service
agency.
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