During this week end I have been beginning to repair our unit of HP54501a oscilloscope from the early nineties.
What a design! The main circuit and all the other circuits (keyboard, power supply, CRT driving circuits) are of exceptional design. The main circuit is built around a Motorola 68000 microprocessor, and the layout and the PCB itself are incredibly beautiful and well done. This is the quality of HP of that era, second to none.
Also the clarity of the manuals and the accompanying documents is exceptional. You get a course on oscilloscope basics for free when you read them!
I will post updates as the repair go. Suffice to say that the self test information was extremely clear and conducive to an easy diagnostic.
More on next issues...