A Positive Temperature Coefficient (PTC) Protection





A.1 PTC Component

The SCSI termination power on the FSBE/S SBus card is protected with a positive temperature coefficient (PTC) component. This component acts somewhat like a fuse.

A PTC will sense excessive current and increase its internal resistance to reduce the current to an acceptable level. The PTC will restore a circuit to normal operation once the potentially harmful condition has passed. In contrast, a fuse shuts down a circuit when a harmful condition first occurs, and that circuit remains shut down until the fuse is replaced.

A.2 PTC Reset

If a PTC component (fuse) on the FSBE/S card shuts down a circuit, do the following (refer to Figure A-1):

    1. Turn off the power to the system.
    2. Correct the potentially harmful condition.
    3. Allow 20 seconds for the PTC to reset.
    4. Turn on the power to the system.

    Figure A-1 Location of FSBE/S SBus Card Fuse