Removal And Replacement Strategy; General Cautions During Removal And Replacement; Electrostatic Discharge - HP LaserJet PRO M521 Repair Manua

Removal and replacement strategy

General cautions during removal and replacement

This chapter describes the removal and replacement of field-replaceable units (FRUs) only.
Replacing FRUs is generally the reverse of removal. Occasionally, notes and tips are included to
provide directions for difficult or critical replacement procedures.
HP does not support repairing individual subassemblies or troubleshooting to the component level.
WARNING!
attempting to service the product. If this warning is not followed, severe injury can result, in addition to
damage to the product. The power must be on for certain functional checks during troubleshooting.
However, disconnect the power supply during parts removal.
Never operate or service the product with the protective cover removed from the laser scanner
assembly. The reflected beam, although invisible, can damage your eyes.
The sheet-metal parts can have sharp edges. Be careful when handling sheet-metal parts.
CAUTION:
not straighten prefolds in the FFCs. You must fully seat all FFCs in their connectors. Failure to fully seat
an FFC into a connector can cause a short circuit in a PCA.
Incorrectly routed or loose wire harnesses can interfere with other internal components and can become
damaged or broken. Frayed or pinched harness wires can be difficult to find. When replacing wire
harnesses, always use the provided wire loops, lance points, or wire-harness guides and retainers.
NOTE:
To install a self-tapping screw, first turn it counterclockwise to align it with the thread pattern,
and then carefully turn it clockwise to tighten. Do not overtighten. If a self-tapping screw-hole becomes
stripped, repair the screw-hole or replace the affected assembly.
Note the length, diameter, color, type, and location of each screw. Be sure to return each screw to its
original location during reassembly.
TIP:
For clarity, some photos in this chapter might show components removed that would not be
removed to service the product. If necessary, remove the components listed at the beginning of a
procedure before proceeding to service the product.

Electrostatic discharge

CAUTION:
when removing product parts. Always perform service work at an ESD-protected workstation or mat, or
use an ESD strap. If an ESD workstation, mat, or strap is not available, ground yourself by touching the
sheet-metal chassis before touching an ESD-sensitive part.
Protect the ESD-sensitive parts by placing them in ESD pouches when they are out of the product.
2 Chapter 1 Removal and replacement
Turn the product off, wait 5 seconds, and then remove the power cable before
Do not bend or fold the flat flexible cables (FFCs) during removal or installation. Also, do
Some parts are sensitive to electrostatic discharge (ESD). Look for the ESD reminder
ENWW