Edited to add: For those of you who couldn't access the video earlier, it seems to be working again. Enjoy!
I found it on The Documentary Blog. It's the kind of weird shit I love.
Here are a few more terrifying TV logos:
Here's a freaky one I remember. It's not really a logo, but I think it fits. The thing is, most of the times I saw it, it was followed by a show aimed at kids like a Peanuts cartoon or an episode of The Muppet Show.