[Retrorepair]

Gotcha. The manual literally makes it look like (to me anyway) you need to move back and forth.

Well I had a crack last night and I think the act of moving the chassis out and putting it back in has made the flybacks "fizzing" worse. I felt a tingle as I was going to move the chassis and realised it was the HT cable. I then noticed visible arcing at the top of the flyback so think it's time to replace it before I go any further. It does look as if there has been arcing there for a while as it looks a little burned on top so guess there's a crack under the rubber cap.

I did try to focus anyway since it was making this noise before to no real ill effect but literally when it gets close to good focus, the tube neck audibly rings like a fire bell!

I'll get a replacement and report back.