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LG Optimus L70 Troubleshooting
Phone screen frozen or unresponsive
Plug the phone into charger.
Replace the battery. For information, see the Replacement Wiki here.
Test the charger on another device.
If the screen is not responding, try charging it in another outlet.
Try plugging another device into the outlet to make sure the outlet is supplying power.
Be sure that the charging port and cable are free of debris.
Replace the logic board. See the the Logic Board Replacement Wiki here.