Laser Printers
Laser printers use a laser beam to create an electrostatic image on a photosensitive drum, which then attracts toner (dry powder) and transfers it to paper where a fuser unit melts it permanently into the paper fibers using heat and pressure.
Advantages: Fast print speed, sharp crisp text, low cost per page, long-lasting prints that don't smear. Best for high-volume office printing of documents. Disadvantages: Higher upfront cost, toner cartridges are expensive to replace, needs warm-up time (fuser), produces ozone (ventilate the room), paper exit is warm.
Key components: Imaging drum (photosensitive OPC drum), toner cartridge, fuser assembly (contains heat roller and pressure roller), corona wire or charge roller (charges the drum), transfer belt/roller (transfers toner to paper), laser scanning assembly.
The Laser Printer Imaging Process — 6 Steps
The laser printer imaging process is one of the most tested topics on the CompTIA A+ exam. Know these six steps in order:
Remember the six steps as: Processing → Charging → Exposing → Developing → Transferring → Fusing
A common mnemonic: "Please Charge Every Dragon That Flies" or "People Can Experience Dramatic Technology Failures." The A+ exam may describe a failure symptom and ask which step caused it. For example: ghost images on the page = fuser or drum cleaning failure (toner from a previous page wasn't fully cleaned). Toner smearing when touched = fuser failure (toner not bonded).
Laser Printer Troubleshooting
| Symptom | Most Likely Cause | Solution |
|---|---|---|
| Toner smears when touched | Fuser failure (toner not fused) | Replace fuser assembly |
| Ghost / shadow images on page | Drum not cleaning properly after transfer | Replace drum or toner cartridge with cleaning blade |
| Vertical lines down the page | Scratch on drum or debris on drum | Replace toner cartridge / drum unit |
| Blank pages | Empty toner, laser failure, or drum charge issue | Replace toner; check charge roller |
| Speckled / dirty output | Contaminated drum or developer unit | Replace toner cartridge; clean inside printer |
| Paper jams frequently | Worn pickup rollers, damp/wrong paper, debris in path | Replace pickup rollers; use correct paper type |
| Faded print / light output | Low toner, density setting too low | Replace toner cartridge; check print settings |
| Ozone smell | Normal for laser printers; excessive = corona wire issue | Ensure ventilation; replace corona wire if excessive |
Inkjet Printers
Inkjet printers spray microscopic droplets of liquid ink onto paper through tiny nozzles in the print head. The print head moves back and forth across the paper on a carriage belt assembly. Two technologies: thermal (bubble jet) — a tiny heating element vaporises a small amount of ink to form a bubble that forces a droplet out (HP, Canon); piezoelectric — a piezo crystal deforms when voltage is applied to push ink out without heat (Epson, many professional printers).
Ink types: Dye-based inks produce vibrant colours but are less water-resistant and fade faster. Pigment-based inks (used in photo and document printers) are more water-resistant and fade-resistant. Ink cartridges dry out if the printer is left unused for weeks — the nozzles clog. Run the printer's built-in head cleaning utility to clear clogged nozzles.
Thermal Printers
Thermal printers use heat rather than ink or toner. There are two distinct types that the A+ exam distinguishes between:
Direct thermal: The print head applies heat directly to heat-sensitive paper that darkens when heated. No ink or ribbon is required — just the special paper. Used for receipts, shipping labels, and barcode labels at POS terminals. Limitation: the paper fades over time and will darken if exposed to heat (a receipt left in a hot car may turn completely black). Cannot be used for permanent records.
Thermal transfer: The print head heats a wax or resin ribbon, melting the ink from the ribbon onto the label media. Produces durable, long-lasting prints that resist heat, moisture, and chemicals. Used for product labels, asset tags, barcode labels, and wristbands that need to survive harsh environments. More expensive than direct thermal but produces permanent prints.
Impact Printers (Dot Matrix)
Impact printers work by physically striking an ink ribbon against paper using a print head containing a matrix of tiny metal pins. The pins form characters and images by selectively striking. Impact printers are noisy but remain in use in specific applications because of their unique capability: they are the only printer type that can print on multi-part carbon copy forms (impact copies through multiple layers simultaneously).
Common use cases: invoices, receipts, and forms that require simultaneous carbon copies (banking, auto repair shops, warehouses, industrial environments). Also used in environments where paper may get wet or dirty, and where toner/ink-based printers would fail.
Printer Type Comparison
| Property | Laser | Inkjet | Thermal | Impact |
|---|---|---|---|---|
| How it works | Laser + toner + fuser | Liquid ink droplets | Heat on special media | Pins strike ribbon |
| Consumable | Toner cartridge | Ink cartridge | Thermal paper / ribbon | Ink ribbon |
| Print quality | Excellent text | Excellent photos | Good (labels/receipts) | Low quality |
| Speed | Fast | Moderate | Very fast | Slow |
| Per-page cost | Low | High | Very low | Low |
| Noise | Moderate | Low | Very quiet | Very loud |
| Best use case | Office documents | Photos, varied media | Receipts, labels | Multi-part forms |
| Carbon copies? | No | No | No | Yes — only option |
Printer Connectivity
The A+ exam tests how printers connect to computers and networks. Common connection types: USB (direct local connection to one computer), Ethernet / wired network (connects to a switch; shared by all users on the network), Wi-Fi (wireless network printer), Bluetooth (short-range, typically for mobile devices), and USB print server (a device that connects a USB printer to a network, making it network-accessible).
When installing a network printer in Windows, you can add it via Settings → Devices → Printers & scanners → Add a printer or scanner. Windows will detect network printers automatically, or you can add by IP address. Each printer requires a driver — software that translates print jobs into the printer's language (PCL or PostScript for laser printers).
PCL (Printer Control Language) — developed by HP, used by most office laser printers. Optimised for documents and text. Faster and works well with Windows applications.
PostScript (PS) — developed by Adobe, used in graphic design, publishing, and high-end laser printers. Better at handling complex graphics and fonts. Required for accurate reproduction of professionally designed documents.
Both are page description languages — they describe what should be on the page. The driver converts your document into PCL or PostScript commands that the printer understands.
Exam Scenarios
Studying for CompTIA A+?
Printers are heavily tested — check the full A+ study guide and cheat sheet.