Lighting · Practical guide

LED lights flicker on DMX: what to check and how to test

An LED PAR flashes when you did not program it to, or several fixtures change color as a cue runs. Note when it happens before moving cables or rebuilding the show. That tells you which test to try first: check the signal, compare settings, or inspect the console output. If you change several things at once and the problem disappears, you still will not know which change mattered.

Record where and when the flicker occurs

Note which fixtures fail, where they sit in the chain, and which cue is active. Check whether the flicker is visible to the eye or only on camera: this guide addresses erratic responses to DMX control. Save the show and current settings so you can restore them after each comparison.

Run these tests during rehearsal, with safe access to connectors. Do not open fixtures or alter the electrical installation. To isolate a fixture that behaves erratically, ETC suggests connecting it straight to the DMX source with a short cable, temporarily bypassing intermediate devices and cable runs. Its DMX512 troubleshooting guide.

Record where and when the flicker occurs
What happens	What to compare first
The fault appears after adding a cable run or fixture	Test that run with a known-good cable and check termination
It always fails on the same cue	Compare output values with the fixture’s DMX chart
It works when connected directly	Add cables, adapters and distribution back one at a time
It also fails with a direct connection	Check settings and bring that test result to equipment support

Check cable, termination and each branch

Check the cable type as well as the connector. Two cables with XLR connectors may be built for different jobs: DMX requires cable suitable for data. A microphone cable can pass a short test and fail over a longer run. Replace the suspect section with cable identified for DMX and repeat the same test. The ENTTEC wiring guide explains what to inspect.

Check where each line ends. Termination helps prevent signal reflections at the end of a run; a common DMX terminator has 120 ohms across the data conductors. With an active splitter, each output is an independent line and needs its own terminator at the far end. Terminating one branch does not terminate the others. See the ENTTEC DMX termination guide.

Build a comparison connection
Connect one fixture to the controller with a verified short cable and the specified termination. Select a static scene without strobe and watch whether the response stays steady.
Add one section at a time
Reconnect one cable or device and repeat the test. If the fault returns, record what you added and compare it again before moving on.
Inspect every branch
Check accessible connectors and the final terminator on each line. Use distribution suited to the system; a passive Y cable is not a DMX splitter.
Record what changed and what happened
Keep the stable configuration and the result of each comparison. If you changed both cable and terminator together, you may have restored the line, but that test does not distinguish between those possible causes.

Compare RDM on and off, if your equipment permits

ETC describes devices that misinterpret RDM packets and respond erratically. Check distribution too: RDM needs compatible infrastructure, does not support Y branches, and requires splitters that allow two-way communication. Some interfaces do not offer an off switch. The ETC guide to flicker and RDM helps check those conditions. For RDM, also check controller termination in its manual.

If the port or gateway can disable RDM, record its setting and test the same cue and signal path with RDM on and off. If the behavior improves, review compatibility, firmware and distribution; that result alone does not prove the fixture is damaged. In a mixed system, separating a conventional DMX line from an RDM-capable line may help locate the conflict. Keep both sets of settings for support.

If a cue triggers it, inspect the values being sent

Compare the fixture’s selected mode with the profile in the patch. If they differ, a channel the console treats as color may control another function on the fixture. Some fixtures divide intensity and strobe across ranges of the same channel. Before rerecording the cue, check shutter, strobe and macros in the manual’s DMX chart against the output. ETC explains how the map changes between modes and how parameters can share a channel.

If you need help, send the exact model, mode, address, universe, controller and any firmware details you have. Add a connection diagram and note what happened with the short cable, while rebuilding the line, and when comparing cues. This lets support follow your tests and inspect the section that still fails.

Node Refresh Rate and LED PWM are different settings

If an LED PAR flickers after a console change, first record what changed in the control path. Did it begin when switching to a computer, replacing the node, or running a particular scene? That timing helps prepare a comparison another technician can repeat.

On the ENTTEC ODE Mk3, Refresh Rate controls the repetition of outgoing DMX frames; the manual states a default of 40 fps. PWM frequency belongs to the fixture: Chauvet, for example, publishes 1200 Hz for the Freedom Par Hex-4. These figures describe different processes.

Prepare a fixed scene and watch the fault over several cycles if it repeats. To compare controllers, keep the same fixture and record each setup. If you choose to test another output rate supported by the node, change only that setting and record the result and time.

The test organizes the diagnosis; one improvement still needs to be repeated. If the symptom appears only in a recording, add camera and exposure settings to the record. Do not treat matching numbers as proof of compatibility between devices.

If the output pulses, check Per Address Priority too

If a fixture moves or changes color at regular intervals after connecting a console, note which devices fail and which remain stable. Compare what happens after you stop moving a parameter. That record helps separate the symptom from an assumption about the profile.

If the path uses sACN, identify the receiver and check whether it supports PAP before testing this setting. ETC distinguishes sACN level packets with start code 0x00 from Per Address Priority packets with 0xDD. Some receivers may misinterpret the latter. In Eos Family 3.3.10, Patch > Protocols lets you turn Per Address Priority on or off globally or per universe.

With the network lead, prepare a rehearsal comparison and save the configuration first. If the system supports the change, adjust only PAP and record the response. Keep other conditions the same so the results can be compared.

If it improves, check static scenes, transitions and other sources before keeping the change. A single improvement does not identify the cause. Record the receiver model, firmware and signal path for support if the behavior returns.

When another program joins the network, count the sources

If flicker starts when another program opens, list the senders reaching the node, even before setting up their patches. Compare that count with the receiver limit. As a specific example, the Showtec NET-2/5 Pocket 50808 V1 manual permits up to two network sources per output port; confirm the label identifies that model.

On that node, HTP selects the highest value on each channel; LTP selects the most recently changed value. They do not produce the same result. Save the initial settings and coordinate a rehearsal comparison: open programs one at a time and note when the symptom changes. That record helps trace the path; you must still verify the combination intended for the show.

If lights go out when Wi-Fi drops, check the node output

When the tablet loses its connection, note what keeps working: router, node and line to the fixtures. Check what Hold Last means on that fixture. Losing Wi-Fi on the tablet does not prove that the DMX line stopped transmitting.

For the ODE Mk3 70407, the January 2026 manual says the output repeats the last received frame. In Home, press the universe number to inspect DMX values; Network Stats shows statistics by protocol. Check these readings before and after an agreed control interruption during rehearsal.

Record the time, scene, port and firmware. If values go to black, log that change; if they hold, continue tracing from the output. Do not change Wi-Fi, fixture mode and node settings at once: afterward it will be difficult to tell what made a difference.

Identify Link and Out before swapping cables

If a splitter has similar-looking connectors, note the model and read the panel labels. Draw which cable leaves each port. A photo showing only connectors may miss the distinction you need to check.

The D-SPLIT 70578/70579 has four isolated outputs and two linked inputs. Its July 2025 datasheet allows the line to continue through those inputs.

When investigating flicker, keep that drawing with fixture addresses and modes. Compare one signal path at a time during rehearsal. If you change port, cable and fixture together, it becomes difficult to identify which change affected the symptom.

Frequently asked questions

Does a DMX terminator always stop flicker?

It may correct a fault caused by line termination. If the problem is a cable, fixture profile or cue sending strobe, you will need to check that instead. Compare one thing at a time to see what changes.

Can I use an XLR microphone cable for DMX?

A matching connector is not enough. To build the line or investigate a fault, use cable specified for DMX. An audio cable that works in a short test does not confirm it will work over the event’s cable run.

Should I leave RDM disabled permanently?

Use that change as a comparison when your equipment allows it. If behavior improves, review compatibility, firmware and distribution with the manufacturer before deciding on the final configuration. Record the settings so you can repeat the test.

Are PWM frequency and DMX Refresh Rate the same?

No. On the ODE Mk3, Refresh Rate refers to the DMX output. The published 1200 Hz for the Freedom Par Hex-4 refers to that fixture’s PWM.

What should I record if flicker changes when I replace the console?

Controller model and version, node revision, port used, scene, settings before and after, and time between faults. Also record changes that did not affect the symptom.

Does turning PAP off solve every flicker problem?

ETC documents a possible incompatibility with Per Address Priority packets. Test that setting only as a coordinated comparison for your system. If the symptom changes, record it and review the whole operation before calling the issue resolved.

Where is Per Address Priority in Eos 3.3.10?

Under Patch > Protocols in sACN. The manual documents a global setting and an option per universe. Confirm your version and save the original configuration before comparing.

If each program controls different fixtures, can I skip checking merge?

Still check the sources received by the node. On the Pocket 50808, the documented limit is per output port.

Should I enable HTP for any flicker?

Choose the behavior the show needs and test it. On this node, HTP takes the highest value; LTP takes the most recently changed value.

Does a fixture’s Hold Last guarantee the scene survives a tablet Wi-Fi drop?

Check what the node continues to send. A dropped tablet connection alone does not identify a loss of DMX at the fixture.

Which ODE Mk3 screen helps inspect values?

In Home, press the universe number to see current values. Compare them with Network Stats and the port settings.

Are the two D-SPLIT inputs independent?

They are linked and accept one input signal at a time.

Is every connector labeled Link isolated?

Check the model: the label alone does not confirm isolation.