1971 HMV Trent problem.

[Robert Grant]

Originally Posted by RetroFormat32

Monochrome. We did not get color until 1975.

And a VHF only tuner in a 1971 set?

Would I be right if I guessed you're in Australia?

Okay, I need to ask if your picture is merely off-center (but steady), or rolling (moving up or down the screen and reappearing on the other edge of it).

If it is steady, try the settings on your converter box (usually accessed by the remote control of the converter box) and try different "aspect ratio", "zoom", "display type","shape", "PAL", "NTSC", "50Hz" or "60Hz" settings.

If it is rolling, the sync signal is not as strong as the sync signal on analogue television broadcasts had been. Perhaps try a separate RF modulator (which could be a VCR) instead of the converter box's own.
If your television has valves, try replacing the valve that controls vertical sync.