HP LaserJet PRO M521 Repair Manua page 57

3.
Feed the FFCs and connectors through their retainers.
Figure 1-60
4. Disconnect one screw, and then remove the USB ground wire.
Figure 1-61
ENWW
Remove the document feeder/scanner assembly (2 of 7)
Remove the document feeder/scanner assembly (3 of 7)
Removal and replacement procedures
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