How did the Telstar 525/405-line conversion system from 1962 work?
1960's standards convertors did involve CRTs and cameras, with quite a lot of tweaking to minimise artefacts.
This description of the state of the art at the time, from BBC Engineering, goes into a lot of detail about the process.

Quartz crystals used as delay lines were just around the corner. By 1970 the BBC had built an entire field store based convertor that way. THe references in the linked report show that the design process was already under way in 1964.


Quite a substantial piece of equipment. (picture from RD Report 1970/37 linked above)