OKI B840dn: Setup, Drivers, Ink and Common Problems

Is the OKI B840dn right for you?

An A3 mono LED printer built for engineering offices, schools and anywhere that prints large drawings and spreadsheets in black only. The B840dn is fast at 35 ppm in A4 and takes a large paper stack, and its 20,000-page toner keeps costs reasonable. It is discontinued, so the practical questions for a used unit are drum and fuser life and whether a current driver installs cleanly on your operating system.

Best for: Engineering and school offices printing A3 drawings in mono

Setting up the OKI B840dn

Add the printer by IP and prefer the PostScript driver for CAD output, since line weights and large fills render more predictably than through PCL. Set A3 in the main tray and configure the multipurpose tray for heavier stocks. If Windows 11 rejects the driver installer, install the OKI PCL6 driver via the Add Printer wizard's Have Disk option pointing at the extracted INF file.

1. Unbox and prepare. Remove every piece of shipping tape and packing material, install the ink cartridges, and load paper in the tray.
2. Join your Wi-Fi. Keep the printer close to the router for setup. Most printers only connect to the 2.4GHz band, so if your router broadcasts one merged network name you may need to split the bands temporarily. See our Wi-Fi guide if it will not join.
3. Install the setup app. Use OKI's official app rather than a driver you found on a search result — third-party driver sites are the most common source of printer malware.
4. Add the printer. On Windows 11: Settings › Bluetooth & devices › Printers & scanners › Add device. On macOS: System Settings › Printers & Scanners › Add Printer.
5. Print a test page and run a scan if this is an all-in-one, so you find any problem now rather than when you are in a hurry.

Ink, toner and supplies

The OKI B840dn uses the following consumables. Match the number exactly when you buy: the same printer family often uses several different cartridge numbers by region.

• OKI B840 black toner (20,000 pages)
• B840 image drum (60,000 pages)
• Fuser unit

High-yield (XL) versions almost always cost less per page if you print regularly. On third-party ink and toner, read our honest assessment first, and note that some manufacturers push firmware that rejects non-original chips.

Full specifications