I've just picked up an old Panasonic TX2122 TV. It has a problem with
the picture which shows up as two wide vertical white bars one the
screen, which are obviously some sort of distortion on the signal.
I get this when receiving a picture via RF. However if I play a video
via the video input I get a good picture. I also tried using the TV
tuner on the video to relay a TV station to the video input, but that
doesn't work - it causes lots of interference that seems to go back
and affect the video's RF. I had a working TV connected to the video's
RF output and this destroyed it's picture generating loads of interference.
Looks like its some problem in the RF stages of the TV, any ideas what
I can check?

I'm not sure what chassis this particular TV has, as I can't find
any markings on it.

BTW, its a UK PAL model with teletext.