Clearing the Black Line Print on a Brother DCP-L2550DW

How to Fix the Black Line Print Issue on a Brother DCP‑L2550DW

A black line that appears on every printed page is a common frustration for users of the Brother DCP‑L2550DW. It can be caused by dust, toner residue, or a mis‑aligned drum unit. This guide walks you through the most effective troubleshooting steps and permanent fixes, so you can get clean, crisp prints again.

Understanding the Problem

The black line you’re seeing is usually a horizontal streak that runs across the entire width of the page. It is often the result of:

• Toner build‑up on the transfer roller
• Residue on the drum unit
• Dust or lint trapped inside the printer
• A worn or mis‑aligned print head

Recognizing the source of the line is the first step toward a lasting solution.

Quick Overview of the DCP‑L2550DW

• Printer type: Monochrome laser
• Print speed: Up to 25 ppm (pages per minute)
• Connectivity: USB, Wi‑Fi, Ethernet
• Key components:
  • Toner cartridge (CM, black only)
  • Drum unit (CM)
  • Transfer roller
  • Fuser unit
  • Image‑forming unit (IFU)

Because the toner cartridge and drum unit share a common path, a dirty drum can easily transfer toner residue to the paper. Similarly, a dirty transfer roller can drag toner across the page, creating that unwanted black line.

Preliminary Checks

Before opening the printer, do these simple checks:

1. Power Off – Turn the printer off and unplug it from the wall outlet.
2. Paper Jam – Open the front tray and look for any jammed paper. Clear any obstructions.
3. Print a Test Page – Print a test page from the printer’s control panel. If the line is still present, proceed to the cleaning steps below.

Step‑by‑Step Cleaning Guide

1. Prepare a Clean Workspace

• Lay a clean towel or cloth on a flat surface.
• Gather a microfiber cloth, a soft brush (like a clean paintbrush), and compressed air.
• Keep a small bowl of warm water (optional, for deep cleaning of removable parts).

2. Remove the Toner Cartridge and Drum Unit

1. Open the front cover – Pull the front cover to the side until it lifts.
2. Locate the cartridge holder – The black toner cartridge sits in a cradle that also holds the drum unit.
3. Release the cartridge – Gently pull the cartridge and drum unit out.
4. Set aside – Place them on the clean towel. Do not touch the rubber seals on the cartridge.

3. Inspect the Drum Unit

• Look for visible toner – If you see a layer of toner on the drum surface, it’s time to clean it.
• Check the roller – The drum’s roller can become dusty or worn.

Cleaning Method A: Soft Brush

1. Hold the drum unit so that the toner side faces away from you.
2. Use the soft brush to gently sweep the drum surface in one direction.
3. Repeat until the toner layer is removed.

Cleaning Method B: Clean Cloth

1. Dampen a microfiber cloth with a small amount of water or rubbing alcohol.
2. Wipe the drum surface gently, moving in one direction.
3. Allow the drum to dry completely before re‑installing.

4. Clean the Transfer Roller

1. Locate the transfer roller – It is a small, circular component near the drum.
2. Use a lint‑free cloth – Gently wipe the roller in a single direction.
3. Optional – If the roller is heavily coated, use a mild solution (water or isopropyl alcohol) with a cloth.
4. Dry – Ensure the roller is dry before re‑assembly.

5. Use Compressed Air

• Target the fan – Blow compressed air into the fan area to remove dust.
• Avoid spraying – Spray directly at the fan blade; don’t use a hose, as it can force dust deeper into the printer.

6. Re‑install the Cartridge and Drum

1. Insert the drum unit – Slide it back into the cradle until it clicks into place.
2. Insert the toner cartridge – Align the cartridge’s notch with the holder and push until it locks.

7. Power On and Test

• Plug the printer back in and power it on.
• Print another test page.
• Observe the output. If the black line is gone, you have successfully resolved the issue.

When Cleaning Is Not Enough

If the line persists after thorough cleaning, consider the following deeper fixes.

A. Replace the Drum Unit

A worn drum can develop micro‑cracks that allow toner to cling and spread. Replacement usually resolves the issue.

1. Purchase an OEM drum – Ensure it’s the correct model for the DCP‑L2550DW.
2. Follow the same removal steps as above.
3. Install the new drum – The new unit should be dust‑free and ready to use.

B. Replace the Toner Cartridge

Occasionally, a defective cartridge can cause streaks. Replacing it is straightforward:

1. Unplug the printer – For safety.
2. Remove the cartridge – As described earlier.
3. Insert the new cartridge – Align and lock.
4. Reset the counter – Some printers require resetting the toner counter via the control panel.

C. Check for Internal Misalignments

• Inspect the image‑forming unit (IFU) – If the IFU’s rollers are bent or mis‑aligned, they can drag toner across the paper.
• Consult a professional – If you’re uncomfortable opening the IFU, contact a certified Brother technician.

Maintenance Tips to Prevent Future Lines

1. Keep the Printer Clean – Wipe the exterior with a damp cloth regularly.
2. Use Good‑Quality Paper – Cheap paper can lead to increased dust and toner residue.
3. Avoid Extreme Temperatures – Store the printer in a cool, dry place.
4. Schedule Periodic Cleaning – Every 300 pages, clean the drum and transfer roller.
5. Update Firmware – Keep the printer firmware current to prevent software‑related printing glitches.

Common Questions

Final Checklist

• [ ] Clean the drum unit with a soft brush or cloth.
• [ ] Wipe the transfer roller with a lint‑free cloth.
• [ ] Use compressed air on the fan.
• [ ] Re‑install the cartridge and drum.
• [ ] Print a test page.
• [ ] Replace drum or cartridge if necessary.
• [ ] Perform regular maintenance.

By following these detailed steps, you’ll eliminate the black line from your Brother DCP‑L2550DW and enjoy clean, professional prints. Regular upkeep and timely replacements keep your printer operating at peak performance, saving you time and frustration in the long run.