Modifying a B&W TV for composite video input

It's fun until you start working on a live-chassis set and you suddenly apply mains across your video interface circuit and yourself.... Seriously, many large-screen (non-portable) B&W TVs have a live chassis connected directly to one side of the mains (or worse to one side of a bridge rectifier connected to the mains, so the chassis sits at half mains voltage on average). Don't even think of adding a composite input to such a set unless you connect the mains input to the secondary of a double-wound isolating transformer. (OK, it is possible to isolate the video input rather than the mains -- Radio Shack did on the original Model 1 monitor, which has a hot chassis. But this is a lot harder to get working right, and a lot more dangerous to experiment with). Portable TVs that can also run off a 12V battery _normally_ have an isolated PSU, but please check to be sure... A circuit diagram of the set is _essential_. I am not sure where you are -- if you're in the States, get the Sams Photofact for the set if you can't get the original service manual. If you're in the UK, see if it was covered in 'Radio and Television Servicing'. Then all (!) you need to do is find the video detector stage and feed in your composite signal at the output of that stage. Hopefully the sync separater takes it's feed after that point (it's almost certain you can find a point where this is the case) so you really can feed in a composite signal and expect it to work. -tony