This is the Samsung Metro B312E Solution for Not charging problem or it shows no charging indication when the battery charger is plug-in. The solution below shows the charging connection line paths which can be used for easy troubleshooting or repair the Samsung SM-B312E charging problem.
For Charger No Response or Indication problem, you may first check the charging pin connector for possible damaged, bended or lifted pin solder pads. The center pin holds the positive voltage of the charger and the side pin which is for the negative or ground lines.
Then check the fuse and the and the diode, replace if found damaged.
Now re-solder charging connector pins and check.
Check charging voltage with the help of multi meter. Place Negative terminal of multi meter on ground and Positive on a charging pin (1st pin from your left hand side).
Make sure that the voltage is between 5V to 5.5V, if it is not then replace charging connector. (Charging Connector can be replaced by heating it from the opposite side of the board, while heating it, pull charging connector with the help of Tweezers).
Now remove metal sheet covering the charging section (It contains Charging IC and Components).
Check continuity between Fuse and Charging Pin (1st from your left hand side). If there is no continuity, place jumper.
Heat charging IC, if it is faulty then replace it.
Now check charge at the battery terminals, if it is not standard voltage then re-solder or replace battery terminals.
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