Power and volume button schematic for the Samsung SM-A21s in PDF form, 3.82 MB. It shows the key circuit for the on/off and volume controls, usually the side-key connections and the lines back to the power management and processor side. Useful when the phone will not power on from the button or volume keys do nothing: check button continuity, look for shorts on the key lines and test the flex connection. Opens in a standard PDF reader. Make sure the board is from an SM-A21s before using it.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @phoneSchematics. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.