If you own a laser printer and you're seeing poor print quality — ghosting, lines, white streaks, or speckled output — the instinct is to replace the toner cartridge. That's understandable, because toner is the part that runs out. But toner failure and drum failure look different, and confusing the two is an expensive mistake. A replacement toner cartridge typically costs £15–£35. A replacement drum unit costs £30–£80. Replacing the wrong one and then having to buy the other is a frustrating and avoidable outcome.
What Is Each Part?
The toner cartridge contains the fine powder (toner) that forms the image on the page. It's consumed with every print and needs replacing when it runs out. On most consumer laser printers (especially from Brother and Samsung), the toner cartridge is a separate unit from the drum.
The drum unit (also called the imaging drum or OPC drum) is a photosensitive cylinder that receives the laser beam to create the electrostatic image, which then attracts toner and transfers it to paper. The drum isn't consumed by printing in the same way toner is — it wears out over a longer period, typically 12,000–30,000 pages depending on the model.
Some printers — particularly HP LaserJet models and many Canon units — combine the toner and drum into a single cartridge. If yours does this, the distinction doesn't apply; you replace both components at once. Check your printer's consumables page to see whether yours uses separate or combined units.
Signs the Toner Is the Problem
- Prints are uniformly faded or washed out across the full page
- The printer is reporting a low or empty toner level
- Fading is consistent from the first page to the last
- Shaking the cartridge temporarily improves output (confirms toner is nearly depleted)
- No repeating defect pattern at a fixed interval
Signs the Drum Is the Problem
- Ghosting: a faint, repeated echo of an image appearing on the page at a fixed interval
- Black or white lines running vertically down the page (parallel to paper travel direction)
- Random black specks or toner scatter that appears consistently
- A scratched or damaged appearance on the visible portion of the drum surface
- The defect repeats at a consistent interval equal to the drum circumference (usually 75–95mm)
Print a test page and measure the distance between a repeating defect. If it matches the drum circumference (found in your service manual or by measuring the drum itself), the drum is the cause. Toner defects don't repeat at fixed intervals.
Extending Drum Life
Drum units last longer than most people realise if treated correctly. The main killers are light exposure (never leave the drum unit in bright light for more than 5 minutes), scratches (never touch the green or blue drum surface), and poor-quality toner (compatible toner cartridges with coarser particles accelerate drum wear). If you print infrequently, a drum unit bought today could last 3–5 years.
What the Error Codes Are Actually Telling You
Most laser printers display different codes for drum and toner issues. On Brother printers, a "Replace Drum" or "Drum End" message specifically refers to the drum unit, while "Replace Toner" or "Toner Low" refers to the cartridge. On some models, the drum life counter must be manually reset after replacing the drum — check your printer's manual for the exact button sequence, as forgetting this step causes the "Replace Drum" message to persist even with a new unit installed.