This one started as: “The stage lights are playing up again.”

A public building in the Colchester area had a DMX stage lighting system feeding a mix of moving-head “robot” lights and uplighters. Some fittings wouldn’t come on, others worked intermittently, and the mixer desk kept “forgetting” the sliders.

On jobs like this, you’re really fault-finding two systems at the same time:

  • The extra-low-voltage (ELV) control side – DMX over XLR/XMR cabling.
  • The mains electrical installation feeding it all.

What was going wrong on the DMX side

Once I’d traced the line and done some basic checks, a few issues showed up quickly:

  • Damaged cabling between outlets – several of the XLR runs between wall outlets had physical damage: crushed sections and poor terminations. That’s enough to cause intermittent data faults and random behaviour on a DMX line.
  • Damaged patch leads to the lights – the leads from outlets to multiple “robot” uplighters were also in poor condition. Move the cable and the light would drop off the universe or flicker.
  • Fixtures that had lost their addresses – a number of the uplighters had lost their DMX addresses, so they were no longer listening where the desk expected them to. On a mixed system, that quickly turns into “nothing is doing what the sliders say”.
  • A faulty plug into the mixer desk – the XLR plug on the entry into the desk was cracked and poorly terminated, giving another intermittent fault right where the signal starts.
  • Mixer desk losing its memory – the desk itself wasn’t holding on to its programming. Inside, the backup battery had leaked onto the PCB. That battery wasn’t realistically serviceable in situ and, once electrolyte has leaked on the board, reliability is gone even if you can physically change it.

What I did on the day

On the control side I:

  • Repaired and/or replaced damaged ELV (DMX) cabling where it was practical to do so.
  • Re-addressed the affected fixtures so they lined up again with the console’s channel layout.
  • Confirmed the mixer desk had a hardware fault due to a leaking backup battery and recommended replacement rather than attempting to rescue it.
  • Showed the client how to re-create a basic show layout (key addresses and channels) if the desk loses power or forgets its memory again, and left a simple printed step-by-step guide with the console so staff can recover a workable setup for events until the desk is replaced.

The end result on the day was a working (but clearly tired) system, with a clear recommendation that the controller itself needs replacing.

The more serious part: electrical safety issues

Alongside the DMX faults, there were a number of mains electrical issues that shouldn’t have been there – and certainly not in a public building.

These sections had been installed by AV contractors rather than electrical installers. Issues included:

  • 230 V and ELV control sharing the same back box and plate – mains lighting supply (Band II) and extra-low-voltage control cabling (Band I, e.g. DMX) were running into the same back box and faceplate with no internal barriers or compartments. There was only basic insulation and roughly 20–40 mm of air between terminations.
  • Home-made XLR inlets/outlets next to 230 V power – DIY XLR inlets and outlets on plates that also carried 230 V twist-style power connectors. On the rear, some of the terminations were just spade connectors that were barely attached.
  • Poor access – outlets hidden behind pillars – many of these plates were tucked behind pillars or in other hard-to-reach spots. That makes inspection and maintenance difficult and encourages more bodging over time.

None of this is the sort of thing you want hidden in the fabric of a building that’s open to the public.

On the day I:

  • Repaired the ELV control wiring sufficiently to restore reliable operation.
  • Documented and explained the electrical safety concerns to the client in plain language – where they were, why they’re a problem, and what the risks are.
  • Recommended a full replacement of the mixer desk rather than attempting to repair a unit with a leaking battery and damaged PCB.

Our recommendation to the client

After restoring an acceptable level of operation, I provided a quotation to:

  • Replace the existing mix of plates with proper, compliant outlets that keep mains and control wiring correctly separated.
  • Install more rugged cabling and connectors designed for repeated plugging/unplugging and movement.
  • Upgrade to more robust, higher-output fixtures where appropriate, so the system is not only safer but also more capable and easier for staff to operate.

Need help with stage or feature lighting in Colchester?

If you’re running a venue with stage or feature lighting in or around Colchester and you’ve got unreliable or “possessed” DMX behaviour – or concerns about how AV and electrical work have been mixed over the years – I can:

  • Fault-find the existing setup.
  • Make sensible repairs where possible.
  • Design and quote for a safer, more robust replacement that respects both the show and the Wiring Regulations.