Did you make sure to snip the wire coming UP from the board, to the center conductor?
There's also an RC-bridge connecting from bottom right-corner inside the RF Modulator can, going to the center conductor. . . . T
I did snip the center conductor clean before attaching the jumper. In fact that was the hardest part of the operation. (Very difficult to get at with any tools.) Finally used a pair of my wife's eyelash trimmers to cut the RC bridge out. Upon close inspection of the last picture you can see the RC bridge is now gone. I had tried to just snip it and push it slightly out of the way but a quick continuity check kept showing a short until I completely removed the RC bridge. If I wasn't positive no video signal is now leaving the T1000, I might fiddle with it some more, but since I already had some keys that weren't working, I'm just going to give up on it.
I've already found a new use for it though. I use it as a wedge to chock the back wheel of my car when the front end is raised up, so the car doesn't roll backwards. Very handy
Besides, this gives me an excuse to use with the wife, on why I now need a replacement - maybe a ZX80 or ZX81 or some other Sinclair machine.