I managed to find some internal images on a backup disk and these are probably of my main TR4172. The pictures are really fuzzy but I was in the middle of faultfinding so they were taken in a hurry. it looks like the camera didn't focus properly.
I've uploaded some of them here.
https://www.qsl.net/g/g0hzu//RF%20Tr...ctures/TR4172/
These show that this analyser is a bit different to the one shown in the service manual. If you look at all the images there are some piggy boards with printed filters on them in the LO section so this looks a bit bodgy in places to me.