Power and volume key circuit for the Samsung SM-A12 (Galaxy A12), presented as a 3.39 MB PDF schematic section. It shows how the on/off and volume buttons connect through the side-key flex to the PMIC and processor, which helps with a dead power key, stuck volume buttons or a phone that boots only on a charger. Measuring the key lines for the expected voltage and a clean drop when pressed is the usual check. The model suffix and board revision are not stated, so verify them on your handset first.
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