[jimmc101]

Thanks for the reply.

The 'Horiz drive' goes to a driver transistor which is transformer coupled to the line output stage. To my untutored eye the whole circuit looks very similar to a section of a monochrome TV of that era.

Having spent some time looking at the construction of the analyser it looks as if it is more easy to access display module than the video processor so that's my plan for tomorrow.
Construction is similar to A7550 as shown in the attachment.

Jim