OK, here's a copy of the Tektronix 7834 Storage Oscilloscope manual from 1976. I've actually purchased these machines as well as having used them. These are Internet Archive links:
https://archive.org/details/tektronix_7834 (Main manual)
https://archive.org/details/tektronix_7834-op (Options manual (small, but good for photographs).
Here is a collection of other Tektronix manuals (I've used quite a number of these devices too over the years and many of these manuals are of the same or similar excellent quality as the 7834 (the reason I chose the 7834 is that it was the first to mind but it could easily have been another device from Tek).
https://archive.org/details/manuals_tektronix
These Tektronix manuals are truly superb—world class—and you'd be hard pressed to find better anywhere else. The things to keep in mind are their excellent indexing, clarity of circuit board diagrams including grided cross references on diagrams, the comprehensive parts and spares lists, the clarity of circuit diagrams and the excellent descriptions of the device's operation, etc. (I'm not alone in thinking this way either, the fact that these manuals are on the I.A. and that so much space is devoted to them is testament to that.)
Here's another device that I just thought of and which I'm familiar: 7L13 Spectrum Analyzer:
https://archive.org/details/tektronix_7L13
The 7L13 manual if anything may be marginally better because of the photographs and the labeling is a whisker better in some instances. The 7L13 file size is 56,832,819 bytes.
Note, whenever downloading Tek manuals for the Internet Archive keep in mind there are usually multiple copies from the same common link and they're of varying quality. Always choose the best quality manual. For example, I have two copies of the 7834 manual as PDF files which I downloaded ages ago from the I.A., one is 12,338,193 bytes and the other is 61,818,166 bytes (I assume they are still the same on the server); clearly the latter is better so make sure you get that version.
Happy reading! ;-)