[old_tv_nut]

"Noise gate" adjusts where the sync circuit starts to ignore high amplitude RF interference, and you don't have any. You need to find the real AGC adjustment if there is one.

The IF would have to be modified to a whole different configuration -it's not just that it's a SWIF, but also may be that it has separate video and audio second detectors, each fed by a different IF response, or other complex fooling around.