739 Troubleshooting Guide9 Troubleshooting Guide9.1 Requirements Before Contacting Samsung CustomerService Center9.1.1 Testing the ProductBefore calling Samsung Customer Service Center, test your product as follows. If the problem persists,contact Samsung Customer Service Center.Check if your product is operating normally by using the product test function.If the screen is turned off and the power indicator blinks even though the product is properly connectedto a PC, perform a self-diagnosis test.1 Power off both the PC and product.2 Disconnect the cables from the product.3 Power on the product.4 If the message Check Signal Cable appears, the product is working normally.If the screen remains blank, check the PC system, video controller and cable.9.1.2 Checking the Resolution and FrequencyFor a mode that exceeds the supported resolution (refer to "10.5 Standard Signal Mode Table"), themessage Not Optimum Mode will appear for a short time.9.1.3 Check the following.Installation issue (PC mode)Issues SolutionsThe screen keeps switching on and off. Check the cable connection between the productand PC, and ensure the connectors are locked.(Refer to "2.2 Connecting and Using a PC")