Before you buy a new cell phone or new tablet, please try the following procedure to repair your device. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card. It is impossible to recover your data after doing a hard reset, so online backup is always important. For all of your data, a backup should be done on an external device, hard drive, raid system or media. With or without insurance, if your cell phone lost, damaged or stolen at least your invaluable data is backed up in a safe place.
Samsung Galaxy S 4 hard reset
force reset Reset the device: Press and hold for more than 7 seconds to reset the device if it has fatal errors or hang-ups, or freezes.
sgs4 hard reset or reset Galaxy S4: PRESS AND HOLD VOLUME UP + Home Button + Power. Keep holding HOME + Volume UP, but after vibrate release power.
Unlock Galaxy S4 using hard reset
Turn the phone off.
Press and hold VOLUME UP and Home (middle) button
Press Power until the phone vibrate
Wait until you see the Android logo then release all the buttons.
Select Wipe data/Factory reset with VOLUME DOWN, press Power (right hand-side)
Select YES -- delete all user data with VOLUME DOWN and then press Power
After format, press Power again to reboot phone. (select reboot system now)
Turn the phone off.
Press and hold VOLUME UP and Home (middle) button
Press Power until the phone vibrate
Wait until you see the Android logo then release all the buttons.
Select Wipe data/Factory reset with VOLUME DOWN, press Power (right hand-side)
Select YES -- delete all user data with VOLUME DOWN and then press Power
After format, press Power again to reboot phone. (select reboot system now)
unlock i9500 galaxy samsung cell phone red triangle exclamation mark
or
If your device is frozen and unresponsive, press and hold 
for 7 seconds. The device will reboot automatically.
If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select
Settings - Accounts - Back up and reset→ Factory data reset → Reset device→ Erase everything.
for 7 seconds. The device will reboot automatically.If this does not solve the problem, perform a factory data reset. In Idle mode, open the application list and select
Settings - Accounts - Back up and reset→ Factory data reset → Reset device→ Erase everything.
or Factory format entering sgs4 format code
Use this method to hard reset your Samsung Galaxy S 4: Enter *2767*3855#. Warning! All your data including contacts, messages etc. will be lost! Copy all your necessary data/Contacts/Messages etc. to SIM or make backup to your PC before full reset! Take out SIM card before full reset.
Note: If you reset your device to the factory defaults with SD card encryption setting enabled, the device will not be able to read your encrypted files. Disable this setting before resetting the device.
sgs4 firmware flash download mode: PRESS AND HOLD VOLUME down + Home Button + Power on
unlock gs4, how to reset Galaxy S4, sgs4 reset, i9500, resetting gt-i9500, i9505, gt-i9505.
