Getting black screen the last couple of weeks

I thought it was the TV and bought a new TV. It still does the same thing. No rhyme or reason the screen goes black. I re-start the cable box and it returns to normal. The old TV works fine if I just plug it in without the the cable box it turns on and plays DVD. Not surprising since the cable box is older than the hill and the remote battery lid keeps falling off. I'm keeping it on with scotch tape. I tried to contact Comcast to get it swapped but the chat bot just gives me the runaround. There's no chat or phone number with real people. Where do I go from here?