Two minutes...is how long it seemed before my Betamax VCR developed issues. I think a dodgy tape has deposited oxide on the heads. I can hear audio but the picture is just noise. It happened after I rewound a tape that was playing perfectly well.
So I now need a head cleaner. Not easy to come by in these enlightened times.
Still, with my VCR being up on blocks I've been forced to tinker with the parameters for Alistair Buxton's VHS-Teletext software. Alistair gave me some pointers and I'm now producing much better output from the Beta VBI files I made before the disaster. I'll leave it to chug through the 1000-odd files overnight, but I should have a few pages from BBC1 1990 to show for it tomorrow morning.
Edit: Here's a test page from the same data set as the one below:
And another interesting looking page: