Direct answer
For the Brother DCP-L2640DW, internal quality output separates hardware/supply from app, driver and color profile. First, print the built-in quality/nozzle/diagnostic page.
What this covers
- Brother DCP-L2640DW (DCP-L2640DW)
- Brother printer; inkjet, INKvestment, monochrome/color laser and label systems use different supplies and codes.
- The specific fault this record addresses: prints faded, streaked, banded or with missing colors
What it does not cover
- ×The same symptom on a different Brother product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
Toner is low or unevenly distributed
What separates it Fading across the page or down one side, gradually worsening.
How to confirm Removing the toner cartridge and rocking it gently side to side redistributes the remaining toner and usually restores output for a while — which confirms low toner rather than a component fault.
- 2
The drum unit is worn
What separates it Repeating marks, bands or fading at a consistent interval down the page.
How to confirm Measure the distance between repeats. Each roller has its own circumference, so the spacing identifies which component is responsible — a diagnostic with no inkjet equivalent.
- 3
The paper is damp or unsuitable
What separates it Patchy output across everything, worse in humid conditions or with paper stored in a garage or basement.
How to confirm Try a fresh ream. Damp paper affects both technologies and is easy to overlook.
- 4
The transfer roller or corona wire is dirty
What separates it Overall faintness across the whole page rather than bands or repeats, with toner known not to be low.
How to confirm Toner is transferred onto the page by an electrical charge, so a contaminated transfer roller or corona wire weakens that transfer and lightens everything uniformly. Some models provide a cleaning slider for the wire; using it is a documented step.
- 5
Toner-save or economy mode is enabled
What separates it Uniformly light output that began without any hardware change, often after someone adjusted settings or a new driver was installed.
How to confirm Toner-save deliberately reduces density and is easy to leave enabled. Check both the printer's own menu and the driver's settings, since either can apply it independently.
- 6
The cartridge is a third-party or refilled unit
What separates it Faintness or inconsistency since changing supplier, with a genuine cartridge previously producing correct output.
How to confirm Toner formulation and charge characteristics vary between manufacturers, and some refilled cartridges do not hold charge consistently across their life.
- 7
The printer is in a very dry or very humid environment
What separates it Quality varying with the season or the room, on a laser printer.
How to confirm Toner transfer is electrostatic, so extremes of humidity genuinely affect it — very dry air increases static and very humid air dissipates the charge that holds toner to the page.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- A nozzle check page on an inkjet, or a print-quality page on a laser — these identify the affected component directly rather than by guesswork.
- Whether marks repeat at a consistent interval down the page, and the measured distance between them.
- Whether one colour is affected or all of them.
- How long the printer sat unused before the problem appeared.
Remove the toner cartridge and rock it gently side to side
ReversibleThis redistributes remaining toner and confirms low toner as the cause if output improves.
Measure the interval between repeating marks
ReversibleEach roller has a different circumference, so the spacing identifies which component is responsible.
Try a fresh ream of paper stored somewhere dry
ReversibleDamp paper causes patchy output on both technologies and is easy to overlook.
Check that toner-save or economy mode is not enabled
ReversibleIt deliberately reduces density and can be set independently in either the printer's own menu or the driver, so check both.
Clean the corona wire using the printer's own slider where the model has one
ReversibleToner is transferred by an electrical charge, so a contaminated wire lightens the whole page uniformly rather than producing bands.
Test with a genuine cartridge if the current one is third-party or refilled
ReversibleToner formulation and charge behaviour vary between manufacturers, and this isolates the supply from the printer.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- DCP-L2640DW. Brother printer; inkjet, INKvestment, monochrome/color laser and label systems use different supplies and codes.
- Type — MONOCHROME LASER all-in-one (no fax)
- A black-and-white laser AIO with print/scan/copy but NO fax (the DCP line drops fax versus MFC). Black-only by design. Laser uses toner and does not clog from disuse.
- Toner & drum are separate
- Separate toner cartridge and drum unit; a drum message/reset is separate from toner. Faded print is low/unseated toner; streaks are the drum.
- Connectivity
- Wi-Fi/USB; 'offline' is usually a network/queue issue.
- Symptom boundary
- This record covers Brother DCP-L2640DW when it prints faded, streaked, banded or with missing colors. A different symptom on the same hardware, or this symptom on a different Brother product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Stop for toner spilling inside the printer, and do not use a household vacuum on toner — the particles pass straight through most filters.
- !Do not run repeated deep cleaning cycles on an inkjet; they consume large amounts of ink and can fill the waste-ink pad prematurely.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. Brother Support publishes this as "Black lines down the page". Brother's own DCP-L2640DW print-quality FAQ (monochrome laser). Found via this model's own live FAQ list, 2026-08-28. What that article does not carry is the model boundary — it is written for a product line, and DCP-L2640DW is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
How do I send a fax from my Brother DCP-L2640DW?+
You can't — the DCP line does not include fax (that is the MFC line). The DCP-L2640DW does print, scan and copy, but has no fax feature, so there is nothing to set up or troubleshoot for faxing. If you need fax, a Brother MFC-series model has it. For everyday black-and-white printing, scanning and copying, the DCP is a reliable, low-cost laser, with separate toner and drum parts.
How do I tell which part is causing repeating marks?+
Measure the distance between the repeats. Every roller in a laser printer has a different circumference, so the interval between marks identifies which component is responsible — a drum, a fuser roller or a developer roller each repeat at their own spacing. That measurement is what a technician will ask for.
Everything prints light but the toner isn't low.+
Check whether toner-save or economy mode is enabled — it deliberately reduces density and can be set in the printer's own menu or in the driver independently, so it is easy to have on without knowing. If that is off, uniform faintness across the whole page points at the transfer roller or corona wire rather than the toner, because toner is held to the paper by an electrical charge that a contaminated wire weakens.
Does humidity really affect a laser printer?+
Yes, more than people expect. Toner is transferred and held by an electrostatic charge, so very dry air increases static and causes scatter, while very humid air dissipates the charge that should be holding toner to the page. Quality that varies noticeably with the season or between rooms is a real effect rather than coincidence.
Does this answer apply to every Brother model?+
No. It is scoped to DCP-L2640DW. Brother printer; inkjet, INKvestment, monochrome/color laser and label systems use different supplies and codes.
What should I record before troubleshooting faded or streaks or banding?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing faded, streaks, banding. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Stop for toner/ink leakage, hot fuser, smoke or damaged cartridges.
Answer for the exact device and software version shown above.