Check The Followings - Samsung ED65C User Manual

Check the followings.

Installation issue (PC mode)
The screen keeps switching on and off.
Blank spaces are found on all four sides of the screen when
an HDMI or HDMI-DVI cable is connected to the product and
PC.
Screen issue
No Signal is displayed on the screen (refer to "Connecting to
a PC").
Not Optimum Mode is displayed.
The images on the screen look distorted.
The screen is not clear. The screen is blurry.
Check the cable connection between the product and PC, and ensure the connection is secure.
The blank spaces found on the screen have nothing to do with the product.
Blank spaces on the screen are caused by the PC or graphics card. To resolve the problem, adjust the
screen size in the HDMI or DVI settings for the graphics card.
If the graphics card settings menu does not have an option to adjust the screen size, update the
graphics card driver to the latest version.
(Please contact the graphics card or computer manufacturer for further details about how to adjust
the screen settings.)
Check that the product is connected correctly with a cable
Check that the device connected to the product is powered on.
This message is displayed when a signal from the graphics card exceeds the product's maximum
resolution and frequency.
Refer to the Standard Signal Mode Table and set the maximum resolution and frequency according to
the product specifications.
Check the cable connection to the product
Adjust Coarse and Fine.
Remove any accessories (video extension cable, etc) and try again.
Set the resolution and frequency to the recommended level.
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