XFinity-Comcast channel programming, Pac-12 Channel 840?, Channel 840 has no picture on any of the 3 cable setups in my house. I can hear the sound, and channels 838 and 841 and, as far as I know, all the other channels work fine. I had the same problem about 3 weeks ago and spent 45 minures on the phone with the Comcast tech. After resetting my cable boxes, modem, and TVs nothing was resolved. I've only tried watching it when CU is playing football, so if it's some kind of blackout, how come I can get the sound. By the way, I can get video and audio on both my phone and on my computer.