DMX Troubleshooting

The basic troubleshooting steps with DMX systems are :

1. Is the DMX chain terminated?

Many people treat the fitting of a termination resistor as optional; but although DMX may work without it, in this state a small change to the DMX network, like adding another cable, may stop the system from working or cause intermittent effects like flicker of dimmers and so on. Ensuring that the last device is terminated can help eliminate these effects.

2. Is the cabling OK?

DMX may continue to work partially even under extreme conditions like having one half of the data pair broken. If you have a dimmer which is misbehaving, take it and connect it directly to the DMX source with a short jumper cable. If it now works there is an issue with your cabling to be investigated. When one wire of the data pair is broken, adding termination will make the problem worse. If you see this, you need to fix the broken cabling, not just leave the terminator off!

3. Is the device OK?

Damage to device DMX receivers (typically a MAX485 IC) can occur in many ways; lightning storms are a common problem. If the device doesn't respond to DMX when connected directly to a known good DMX source via a known good cable, the device itself may need service to repair a damaged DMX input.

Categories: DMX Information pages

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