51.2Color LaserJet Enterprise M751dn

HP Color LaserJet Enterprise M751dn error 51.2: Laser fail

The HP Color LaserJet Enterprise M751dn error 51.2 is a warning related to the laser scanner motor. This prevents the light beam from projecting correctly onto the photosensitive drum. Generally, this failure requires a review of the laser unit. The printer is a robust device for heavy office work.

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Common causes

  • 1Failure of the laser rotation motor.
  • 2Mechanical obstruction in the optical unit.
  • 3Synchronization loss between laser beam and drum.
  • 4Internal disconnection of cables to the laser unit.

Solutions

Quick Diagnosis

The 51.2 error manifests via a screen lock. If the laser scanner does not reach the correct rotation speed, the system detects a communication error and halts.

Step-by-Step Solution

  1. Power off the unit and disconnect it for at least 1 minute.
  2. Check if the printer suffered a recent knock that might have misaligned the laser unit.
  3. Perform a factory reset if possible via the maintenance menu.
  4. If the error persists, confirm the integrity of internal connections to the mainboard.

Prevention and Maintenance

Avoid moving the equipment while powered on or during printing. Excessive environment vibration can affect the laser motor precision. Keeping the surroundings free of fine dust prevents contamination of the sealed optical unit.

When to Call a Technician

This is a critical hardware failure. It requires replacement of the laser scanner unit by specialized technicians, as it involves disassembling sensitive internal parts.

Device Technical Sheet

  • Technology: Color Laser Printer
  • Speed: 41 ppm
  • Connectivity: Gigabit Ethernet
  • Consumables: Genuine HP 658 Toner
  • Use: Corporate
  • Drivers / support