Thanks for the reply! Apologies if this is a double post, but my previous response to this did not appear after I pressed 'Post Quick Reply' and there was no indication that it was waiting for mod approval.
I used a Commodore 64 to provide a stationary image, and
this was the result. It appears that the kink remains stationary but there is some ripple along the sides. The distortion has actually gotten a bit worse since I last turned the set on two days ago, with the middle of the image now being rather out of focus. Please let me know if this video is still too short - I'm scared to run the TV for any length of time lest something go pop!
Cheers