Follow the points within this article to work on one fixture at a time, starting with the first fault in the DMX chain and then working backwards away from the DMX source. Once an issue is resolved, repeat the process until all fixtures are working correctly.
If all fixtures are affected (including the first fixture), this will likely be an issue with the cable between the device and the first fixture.
The DMX standard states that you can chain a maximum of 32 fixtures, this is to make the integrity of the data is kept. This can be maintained using a DMX Splitter. If you are running long chains of fixtures, break up the chain into smaller groups to see if the issue still occurs. If the issue doesn’t occur after breaking up the chain into smaller lengths, increase the number of fixtures connected a section at a time. If the issue comes back, then the DMX signal has likely degraded too much. Consider using a DMX Splitter, which would regenerate the DMX signal and allow for multiple chains of up to 32 fixtures.
Not Functioning Correctly
If the issue occurs halfway down the DMX chain, bypass the previous fixture by connecting the DMX IN and DMX OUT connectors together.
Addressing: If the start address of the fixture doesn’t match the address in the software, then the channels being sent will not control that fixture correctly.
Mode: Some fixtures have multiple modes, enabling different levels of control. If the fixture is supposed to be in 4 channel mode but is actually in 7 channel mode, then you’re going to have problems! A wrong mode will normally look as if the device is partially working. Depending on the start address of the next fixture, you might see a channel overlap where one channel controls more than one fixture in some way.
Other: Some fixtures also feature additional features such as Master / Slave mode, Sound Activation Mode, Preset Mode, Automatic Mode, and Standalone Mode. It is important to make sure that this is off, and the device is set to its DMX channel Mode to allow for DMX control of the fixture via the DMX ports. If the fixture has a factory reset, you could set the fixture back to its defaults. This could flush out any settings that are set on the device that you are unable to locate.
It's important to make sure that all fixtures receive adequate power.
If the fixture is not receiving power, it could also be a blown fuse in either the electrical cupboard, within the fixture, within the plug or within the extension lead.
Many modern fixtures have a power link feature, meaning you can daisy chain power from one fixture to another. If you are using this, check the fixture’s user manual to see the power draw per fixture and that the number of fixtures linked isn’t the cause of this issue.
It is important to make sure that your DMX output device is connected correctly.
Grand Master / BO
Some software has a built in Grand Master or Black Out mode. Depending on the software this might:
Please ensure that the Grand Master (and any potential Sub-Masters) are at full, and any Black Out mode is off.
Status LEDs on the Device can provide you with valuable information regarding what the Device is currently doing.
As there are some differences in terms of Status LED functionality from Device to Device, please view the specific Device's User Manual or Knowledge Base articles.
DMX is a bi-directional digital signal which sends control data through the cable using electrical pulses (square wave). The DMX standard states that the cable must have an impedance of 120Ohms. It is important that only cable of this impedance that is specifically labelled for the use of DMX is used (not audio XLR’s).
When shopping for DMX cables, if it is labelled DMX Cable, then it should meet the specification. Label your DMX cables to help distinguish them from audio cables.
Using any other cable (for example microphone cable) which doesn’t meet the electrical characteristics (impedance & capacitance) as the required specification can cause intermittent errors (strobing / flicking) or irregular operation (loss of signal).
A fault can also occur with a cable if coiled improperly, or if a pin has become loose in the connector. If you suspect a faulty cable or a non-compliant cable is being used, then we recommend that the cable is tested.
To test DMX cables, we recommend the use of a DMX cable tester, if you do not have one to hand, you could use the following steps:
There might be a setting within your show file that is causing the issue.
To rule out any strange issues with the show file settings, create a new show file and patch one fixture which you didn’t have control of and see if you have access to it.
Uninstall / Reinstall the software
There might be a setting within your software that is causing the issue.
To rule out any installation/setting issues with your chosen software, uninstall and reinstall the software - normally this process would reset the software settings.
It is recommended to use the latest version of the software that the developer has released.
There might be a compatibility issue between the software and the device, or a compatibility issue between the software and your fixture.
It is worth checking with another piece of software to see if the issue is isolated to your software.
We would recommend using QLC+ for testing, as it is simple to use. For example, set the Device or Protocol to output within Inputs/Outputs and then use the top row of faders in ‘Simple Desk’ to control each channel.
It is possible that your lights don't support full refresh rates of DMX (40 fps and above).
Some consoles/software provide the ability to limit the refresh rate being outputted from the console/software. You can also limit the refresh rate on the hardware on most of our Devices.
A DMX terminator is a 120-ohm resistor that terminates the DMX signal. If the DMX signal reaches the end of the lighting run and isn’t terminated, the signal can bounce back which will cause interference and lead to flickering lights and loss of control.
Connect a DMX terminator to the DMX OUT at the very last fixture in the chain which terminates the signal.
Some fixtures follow the previous USITT DMX512/1990 DMX standard, which doesn’t support RDM (Remote Device Management) - part of the USITT DMX512-A standard of today. These fixtures can sometimes behave erratically when they receive DMX data with RDM, causing flickering.
Our Devices are split between supporting either USITT DMX512/1990 DMX standard (no RDM) and USITT DMX512-A standard (with RDM). Please see the specific Device's User Manual and Knowledge Base.
With our DMX to USB products:
Merging can also cause flicking, if a device receives more DMX universes than it is expecting to handle then it can cause flickering. Some of our devices can merge DMX Universes.