The technician should reinstall the printer driver software. Continuous pages of random characters usually indicate that the printer is receiving data in an unsupported or incorrectly interpreted printer language. This commonly occurs when the wrong driver is installed, the driver has become corrupted, or a driver configured for a different printer model sends incompatible PCL, PostScript, or proprietary commands. Reinstalling the correct manufacturer-supported driver restores proper translation between the operating system and printer.
DPI settings control print resolution and image detail but do not cause raw characters or command data to print continuously. A toner problem would produce faded, blank, uneven, or smudged output rather than correctly formed random symbols. Updating firmware might help with compatibility in some cases, but the established first corrective action for garbled character output is to remove and reinstall the appropriate printer driver.