When the Lights Won't Turn On: A Practical Stage-Lighting Troubleshooting Guide
There is a moment at every event where a fixture that worked at home goes dark on site. Most failures are not mysterious. They are the result of one variable changing — a different circuit, a loose link in the DMX chain, or a mode setting left on the wrong preset. This guide is a calm, repeatable way to find that variable fast, written for the person holding the controller five minutes before doors.
Last updated: August 2026.
A troubleshooting mindset
Panic skips steps. The reliable method is to isolate one variable at a time, starting from the wall and moving outward:
- Power — is it actually receiving electricity?
- Signal — is a control command reaching it?
- Mode — is it set to listen to the right input?
- Physical — is the cable, mount, or lens the problem?
Work the list top to bottom. Nine times in ten the fault is in the first two steps, not the fixture itself.
Power: nothing turns on, or the breaker trips
If a fixture is completely dark and the display is off, confirm the basics before blaming the unit:
- Test the outlet. Plug a phone charger into the same socket. If that fails, the circuit or the venue's power is the issue, not the light.
- Check the breaker. A tripped circuit breaker is the most common "failure." LED fixtures are efficient, but a full rig on one old circuit still adds up. Spread load across outlets and know your amperage.
- Inspect the IEC lead. The kettle lead at the back works loose in transport. Reseat it firmly; a half-connected lead powers nothing.
The Illuminating Engineering Society treats safe power distribution as part of design, not an afterthought — a chewed or daisy-chained lead is a failure waiting to happen. Where running cable across a room is itself the risk, battery fixtures such as the 12×16W rechargeable par remove that failure class entirely by powering the wash from their own cells.
Powered on, but no light
A lit display with no output almost always means a control or mode issue:
- Sound-active vs DMX. In sound-active mode the fixture ignores the controller and reacts to music; in DMX mode it waits for a signal. If you expected it to follow the board and it is doing nothing, it may be in the wrong mode. The control-mode comparison explains when each is right.
- DMX address. Every fixture on a DMX512 chain — the standard maintained by ESTA — needs a starting address. If two share the same address, they fight; if none match the controller's patched channel, nothing moves. Set a unique address per fixture.
- Termination. Long DMX runs can misbehave without a 120-ohm terminator at the end. For a small rig this is rare, but it is the fix when the last fixture in the chain behaves erratically.
For a grounded walkthrough of addressing and cabling, the DMX512 setup guide is the place to start.
Flicker or unexpected strobe
Flicker has two common sources. The first is power: a weak or shared circuit can sag and cause LED drivers to blink. Move the fixture to a cleaner outlet. The second is the fixture being left in a sound-active or auto mode when you wanted a steady look — switch it to manual or DMX and hold a fixed value. If you are filming, steady light is not optional; see the livestream section of our wedding guide for camera-safe settings.
Wrong color or channels off
When a par shows the wrong hue, check three things: the DMX address (a one-channel offset shifts every color), the fixture profile loaded on the controller (a 7-in-1 system such as the L2700B has several channel modes — pick the one your patch expects), and any master dimmer sitting at zero. Most "dead" color complaints are a dimmer or a mode mismatch, not a broken LED.
Laser not projecting, or haze issue
A laser beam is only visible where it crosses something — usually haze or smoke. If the laser is on but invisible, the room is too clear; add a little water-based haze and the beam appears. If the beam shows but looks weak, confirm the unit is at its rated output and not in a low-power or "free" mode. The L2400 3D RGB laser reads best with a thin, even haze layer rather than a thick fog. Never aim a laser across eye level in a populated area.
App or wireless control won't connect
Wireless control is convenient until the phone and the fixture are on different networks. Confirm both are on the same Wi-Fi, that the fixture is in the correct app-pairing mode (not DMX), and that Bluetooth is enabled where the product uses it. If pairing fails repeatedly, fall back to the onboard buttons or DMX — a rehearsed manual look is more reliable than a flaky connection at showtime. For beat-matched, app-free operation, the music-sync guide covers a sound-active setup that needs no network at all.
A five-minute pre-show checklist
- Power every fixture from a tested outlet; reset any tripped breaker and rebalance load.
- Reseat IEC leads and DMX cables; confirm in/out direction along the chain.
- Set a unique DMX address on each fixture; load the matching profile on the controller.
- Confirm mode (DMX / app / sound-active) matches your plan for the moment.
- Run a full fade up and down; watch for any fixture that lags or ignores a channel.
- For lasers, confirm haze is present and the beam path is clear of eye-level traffic.
Frequently asked questions
My fixture worked at home but is dark on site. Why?
Almost always power or mode. Test the outlet, reseat the IEC lead, and check whether the fixture is in DMX mode waiting for a signal it is not receiving. Home and venue power are rarely the same.
Why does my laser look invisible?
A laser beam needs haze or smoke to become visible. Add a thin layer of water-based haze; without it, the beam travels unseen. Also confirm the unit is not in a reduced-power mode.
Two fixtures are doing the exact same thing unexpectedly.
They share a DMX starting address. Give each a unique address and re-patch the controller so they stop overlapping.
