Composite Companion

The BBC Bridge Companion has RF video output from the factory, but that’s not good enough for its cutting-edge pastel graphics. In order to get things looking their best, I spent a really long time making a composite video mod for the system rather than finishing off my Tetris clone. Reaching into my pile of old homemade boards, I pulled out a second-generation Famicom AV mod board1 and assembled it with a THS7316 video amplifier IC. Obviously, I skipped the audio components, and then hardwired in a yellow RCA female jack. Some ultra-cheap test hooks later, and I had a pretty decent unamplified-composite-video probe! Using this, I figured I’d be able to hook the probe into various spots on the motherboard. By trial and error, I could work out where to grab composite video from before it goes into the RF modulator. New Scope, Who Dis? Of course, none of my candidate points for picking up a video signal seemed to work. I was a little confused, so I shelved it for awhile and then picked…