Samsung UE40T5300 E-Manual page 137

The problem
The PC screen does not appear or it
flickers.
When the PC screen does not appear or the PC is not recognised, check the
power supply of the PC, and then reconnect the HDMI cable between the PC
and TV. When the symptom persists, check that the PC is in Sleep mode.
When the set resolution is not matched, the screen may flicker. For the PC
supported resolution, see 'Read Before Connecting a Computer (Supported
Resolutions).'
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Try this!