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Base checking method:
l Elimination method：Cross test method
Test every function module with Cross test method and locate where the fault in.
l Temperature judgment method：Turn on the POS for a moment. Touch every main IC or the circuit board with hand. Check if there is any IC or circuit board overheating.
l Consolidation method：If you guess the faulty maybe is caused by the solder false, please re-solder it to eliminate the hidden issue.
If the touch screen works in some area, and if it can enter into the settings menu, please enter into menu:
Enable “Show touches” and “Pointer location” option.
Then draw horizontal line and vertical line on the touch screen. Check if it works in everywhere.
If it still has touch screen issue, please check followings:
1) Try to reboot the POS. Check if it has the issue contingently or always.
2) Try to reload the firmware.
3) If it always occur this issue, please check the FPC cable which connect the screen to the mainboard.
Or try to disconnect the cable, and check if the connector has any false. And clean the cable and the connector. Then connect the cable again carefully.
4) Maybe the screen becomes bad. Please try to change the screen.
5) Try to change mainboard with a normal one.
6) If still has the same problem, maybe the problem is on the screen. Then ask manufacture for parts to repair it.