Allen-Bradley I/O Card Component Level Repairs

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We love showing how our repair process works so that customers have a better understanding of what we do when equipment comes through our facility. What follows is a transcription of our YouTube video for repairs of an Allen-Bradley I/O card.


We start with an Allen-Bradley 1746-0A16 output module. With a shorted triac and two burnt traces on this output module, it’s common for a component in an output card to short after a failure occurs from machine-side equipment.


  • Our technician has found two blown traces after visual inspection and uses a meter to ohm out the components.
  • He checks the resistors, optos and triacs to find the bad triacs that need to be marked.
  • An LED inside the optos is turned on using a Huntron Tracker to measure the output of the LED to see if the optos is working as it should.
  • The shorted triac has blown a trace on the backside of the output card in two places, a common occurrence when a component shorts out.
  • The technician is now ready to change out the bad triac with a new one, a component we keep in stock.
  • Next, the technician cleans the blown trace by scraping away the burnt areas and reflowing the two traces that the shorted triac blew out.
  • A red enamel is applied to insulate the repaired trace.
  • Now the output module can be tested in our custom test stand.
  • Our Allen-Bradley PLC custom stand can function-test all SLC500 input and output modules, whether they are triac, DC source, or isolated relay.
  • The technician removes the known, working output module and replaces it with the repaired customer unit.
  • Each switch on the stand represents each input in the PLC, and we test the output of our modules once they receive an input.
  • Our repaired module is functional as it responds to each input signal.
  • The technician can now remove the card from the stand and ship it back to the customer.


Accurately testing is our focus when it comes to Allen-Bradley  repairs. Please feel free to leave any questions in the comments section below, and when you’re ready to speak with our team about your options, head over to to start the quote process!

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