Lighting Fader Not Working? How to Check Your Soft Patch

If you push a fader on your lighting console or software and the light doesn't respond, check the soft patch: the channel or fixture under that fader must be patched to the same DMX universe and start address the fixture is set to, in the DMX mode the fixture is actually using. Before that, rule out the quick causes: grand master, blackout, and which page or fixture the fader is controlling.

What the soft patch does

The soft patch is the table inside the console or software that connects what you control (a channel number or a fixture) to where the data goes: a DMX universe and a start address. It also tells the console which fixture profile and mode to use, so it knows which channel is dimmer, which is red, and which is pan.

The name comes from the days of dimmer racks, when circuits were patched by moving physical cables (the hard patch). Today the patch is software, which makes it easy to change and easy to get wrong. A fader can move perfectly and send values to an address that no fixture is listening to.

Basic 192-channel scene controllers usually have no soft patch. Their patch is fixed: on the common layout of 12 fixture buttons with 16 channels each, fixture 1 starts at address 1, fixture 2 at 17, fixture 3 at 33, and so on up to 177. The fixture's start address has to match the button you use. If you run UKING 192 DMX controller or a similar desk, confirm the start addresses in its manual.

Rule out the quick causes first

• Grand master or blackout. A grand master at zero or an active blackout overrides every fader. On many hardware controllers a blinking blackout LED is the only sign.
• Wrong page, bank, or fixture selection. On consoles, the fader may belong to a different playback page. On 192-channel controllers, faders only control the fixture buttons that are selected, and a page button switches the faders between channels 1–8 and 9–16.
• The fader controls something else. A playback or submaster may be empty or hold different fixtures than you think. Check what is recorded on it.
• Another source holds the channel. Color, position, and other LTP channels follow the latest command, so a running cue or values left in the programmer can override your fader. A parked channel ignores everything until you unpark it.
• MIDI fader pickup. If you use a MIDI controller with software, pickup or soft takeover mode ignores the physical fader until it passes the current software value. Move it through its full travel and watch the on-screen fader.

Check the soft patch step by step

1. Find the patch entry. Open the patch view and look up the fixture or channel on the dead fader. Note its universe, start address, and fixture profile or mode.
2. Read the fixture's display. Compare the address on the fixture's menu with the patch. If the patch says 33 and the fixture shows 017, change one of them to match. Also confirm the fixture is cabled to the output of the universe it is patched on; the right address on the wrong universe still gets no data.
3. Compare the DMX mode. If the patch uses a 14-channel profile and the fixture is set to a 9-channel mode, the fader is sending dimmer values to the wrong channel. Change the fixture's mode or the profile so they match.
4. Check for overlaps. A fixture occupies its start address plus its channel count minus one. A 14-channel fixture at address 1 uses 1–14, so the next one starts at 15. If the second fixture sits at 10, both respond to channels 10–14 and neither behaves correctly.
5. Check universe routing. In the output settings, confirm the universe is assigned to the right USB-DMX interface, Art-Net node, or port, and that output is enabled.
6. Watch the DMX output monitor. Move the fader and watch the value at the fixture's address. If the value changes but the fixture doesn't, the console side is fine and the problem is in the cable or the fixture.

When the patch is right but the light stays dark

• Shutter or strobe channel closed. Many moving heads need the dimmer up and the shutter channel in its open range. A dimmer fader at full does nothing with the shutter at 0. The open range is in the fixture's channel chart.
• Master dimmer at zero. On LED PARs in modes with a master dimmer channel, the red, green, and blue faders appear dead until the master dimmer comes up.
• Fixture not in DMX mode. A fixture running auto, sound-active, or slave mode may ignore DMX. Set it back to DMX mode in its menu.
• No signal reaching it. Check the fixture's DMX indicator, reseat the cables, and make sure the last fixture on the line has a 120 Ω terminator. Keep each run to about 32 devices unless you add a splitter.

Fader fault or patch fault?

Swap things to find out which side is broken:

• Put the same fixture on a different fader or playback. If it works there, suspect the original fader.
• Patch or assign a fixture you know works to the dead fader. If it still does nothing, the fader or its assignment is the problem.
• Watch the output monitor while moving the fader slowly. Values that jump, drop out, or skip ranges point to a worn fader.

A worn or damaged fader on a console or controller needs repair or replacement. Check the warranty and contact the seller's support before opening the unit.

Keep the patch from causing the same problem again

• Keep a patch sheet with fixture, type, DMX mode, universe, and start address, and tape a copy to the controller case.
• Set addresses and modes on the fixtures before load-in and label each fixture with both.
• After any patch change, save the show file and keep a backup copy.
• When you swap a fixture for a spare, check that the spare's mode matches the patch before the show.

FAQ

What is a soft patch in lighting?

It is the software table that links each console channel or fixture to a DMX universe and start address. Changing the soft patch changes where a fader's data goes without touching any cables.

Why does my fader control the wrong light?

Usually because the fixture's start address or DMX mode doesn't match the patch, or two fixtures overlap in address range. Compare the fixture display with the patch entry and check the channel footprint.

Why don't my LED PAR color faders do anything?

In modes with a master dimmer channel, the colors stay dark until the master dimmer is up. Also check that the PAR is in DMX mode, not auto or sound-active.

Do 192-channel controllers have a soft patch?

Most don't. Each fixture button owns a fixed block of channels, so you set each fixture's start address to match its button instead of patching in software.