Lenovo laptop schematic in PDF form for board NM-B521, with the name also carrying the model token x280 and the internal code FN1KR-3. The NM- prefix follows the LCFC numbering used for Lenovo ThinkPad and IdeaPad mainboards. Technicians use a diagram like this to follow power rails from the charger input through the regulators, trace signals between chips and identify parts around a short. Confirm that the NM-B521 number printed on the PCB matches before relying on component references or values. Any PDF viewer with text search opens it.
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