The IR sensor is located on the front of the television. However, are you trying to set up the universal remote? If so the extended needs to be placed in front of the device you are trying to control.
Regards,
HD Tech
http://support-us.samsung.com/cyber/popup/iframe/pop_troubleshooting_fr.jsp?idx=590900&modelname=UN65JU6700F&modelcode=UN65JU6700FXZA
Where is the exact physical location of the IR detector for this TV? I need to place my IR extender at this location. Thanks!

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