DMX Port Not Working on Response Opto or I3M

Symptoms/Issue

One or more DMX ports are not functional

Explanation of Issue

It is likely a DMX chip and/or an opto-isolator has failed, often caused by an external event.

If the opto-splitter is not receiving DMX at all, it is likely the DMX chip at Z1 has failed

If one or more of the DMX ports at A, B, C, D, or E have failed, it is likely the DMX chip has failed. If replacing the DMX chip does not restore DMX for that port, the opto-isolator should also be replaced. All chips on the Opto-splitter are socketed for ease of replacement

Each port also has two fuses for the differential pairs. These should also be checked for continuity, though they rarely fail

The following chart is for the Response Opto-splitter I5M

The image below shows the location of the DMX chips (circled in red) and the opto-isolators (boxed in yellow)

Fix/Solution

1. Remove the Response Opto-splitter from mains power
2. Open the chassis. There should be four Philips head screws
3. Find the DMX chip for the problem port
4. Replace the DMX chip
   1. If replacing the DMX chip does not restore DMX, replace the opto-isolator for the problem port
5. Replace the cover (don't have to screw down the cover yet and plug back into mains power
6. Test the problem port

Parts

Parts can be purchased through ETC or through an electronics distributor, such as Digikey or Mouser (in the United States)