I look at the shit tech manuals around these days (that's if they exixt at all) and can't help but feel how much tech companies have screwed users in recent decades.
My hands-on experience started with the 535 and it was beautifully built, it was a work of art and I still have a plugin for it. So too were the early solid state ones such as the 453 but they were harder to work on.
In my opinion the 'dream range' was the 7000 series, they were easy to work on and like the 535 the manuals are superb. I've used a lot of that series including the 7834 1ns storage unit with various plugins including the 7L13 spectrum analyzer.
In fact, I've still six functioning 7000 CROs including the 7L13 and about a dozen other plugins. An examination of their PWAs show copyright dates in the early 1970s, so that puts these instruments well over 50 years old and the majority have never needed maintenance other than calibration.
In recent years things have changed. With the advent of much cheaper Asian equipment from Anritsu et al Tek had to change to complete, 'bulletproof' engineering unfortunately had to give way to more modest designs.
Reckon those 50+ year old CROs will outlast me. That quality speaks for itself.
_
Edit: Their CRO products were always excellent but I cannot say that about Tek's 1411 modular PAL sync pulse and signal generator. The design was good but it had a build fault, the IC sockets had edge-wiping contacts instead of side-wiping ones which often went intermittent. Not good for a sync pulse gen when say a TV station relies on its output for its whole operation (if the sync gen fails, the whole operation goes black).
There's a long story about that unit, it was returned to Tek for repair under warranty and was still intermittent upon return. So I assigned one of my techs—much to his chagrin—to replace every IC socket (hundreds of them) with the best available-Augat's top gold plated range. From then on the 1411 worked perfectly. Sometimes the best of companies produces a bummer.
I have learned more electronics from the Hewlett-Packard and Tektronix maintenance manuals from before 1990 than from most university courses.
With ancient equipment, like the measurement instruments from Tektronix and Hewlett-Packard, due to having excellent maintenance manuals that allowed a perfect understanding of their internals, it was often possible to find ways to use them for things that had never been foreseen by their designers.
I prefer that very much to the modern instruments that may have a lot of additional features that I do not need, while the features that I do need may have annoying limitations that cannot be surpassed.
Also modern equipment is not strictly only for their original purpose. A lot of modern equipment is hackable now.