I think my new slingbox remote IR cable is bad since I can't change channels on the my COMCAST CABLE Box. I can change it with the Comcast remote but not through the internet slingbox interface. How can I tell if the cable is bad? Should I see a light on end of the IR cable LEDs?
The IR cable light is infrared and not visible to the human eye. Sometimes it can be detected when looking through the viewfinder of a digital camera. You might also check your Slingbox setup to see if the correct brand and model of cable box has been assigned to the SB's remote control.
Yes, IR (Infra Red) signals are not visible to human eye.
So, take a camera (even a mobile camera works), change to video mode and then SEND remote control from virtual remote (from watch.slingbox.com) and observe Blue LED blink at the end of IR blaster which kept infront of Cable box.