Chapter 9 - Troubleshooting
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MNL000303.doc
Revision 2
09/16/2016
SourceSystem TE11
© Versum Materials, Inc. as of the revision and date shown. All rights reserved.
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9.7.2
Troubleshooting Digital Inputs
9.7.2.1
Blown fuse
1. Determine which fuse has blown and remove it from the fuse holder.
2. Turn off power to the system.
3. The digital input circuits are grouped 16 to a fuse. Determine which digital circuits are
associated with the blown fuse and check each one for a short circuit by performing an
ohm test from the fuse output to 24vdc common.
a. If a short circuit exists then disconnect each associated field device, one at a
time, from the interface box, or customer terminal until the short circuit goes
away.
b. If the short circuit goes away then the fault exists in the field device, or field
circuitry. Replace, or repair as necessary. Continue to next step.
c. If the short circuit remains after the field devices are disconnected then the fault
exists in the cables, or connectors somewhere between the PLC Interface Board
and the Interface Box. Replace the cables, or connectors, one at a time, as
necessary until the short circuit is eliminated. Continue to next step.
4. Replace the blown fuse with a new fuse.
5. Re-establish power to the system.
a. If the fuse blows again then more advanced troubleshooting skills may be
required to isolate the fault.