76Chapter 6. TroubleshootingTroubleshootingBefore you contact usBefore calling Samsung Customer Service Center, test your product as follows. If the problem persists, contact Samsung Customer Service Center.DiagnosisCheck if your product is operating normally by using the product test function.If the screen remains blank while the power LED blinks even when the product is correctly connected to a PC, perform product testing.1 Power off both the PC and product.2 Disconnect all the cables from the product.3 Power on the product.4 If No Cable Connected is displayed, the product is operating normally.If the screen remains blank, check the PC system, video controller and cable.Screen ResolutionNot Optimum Mode will briefly be displayed if a mode that exceeds a supported resolution is selected (refer to Supported Resolutions).