I agree to the letter with the by-brand problem descriptions. with one slight exception: I still have a 1968 Motorola tube set (not Quasar) that produced an excellent picture including flesh tones, once the old Motorola CRT was replaced. That set needs a focus resistor now.
I was in high school in the 1970's and we had a vocational electronics class that culminated in TV repair. We fixed small appliances, radios, car radios, stereos, as well as B&W and color TV sets from the 50's through the 70's brought in by students and teachers. We wouldn't allow sets from anyone not connected with the school. A few times TV shops gave us collections of old sets they had been storing that were more costly to fix than their customers were willing to pay. We sometimes combined working CRT's with chassis whose CRT's had gone out, converged them and gave them away. We fixed easy and difficult issues, never butchered a set, and had an arrangement with a shop for the tough dogs. We only charged for parts unless it went to the shop with the arrangement. Parts were very easy to get.
Our class had a full compliment of test equipment: O'scopes, Sencore CRT tester rejuvinator, Sencore tube tester, marker generator, etc.
I had a ball!!!!!
Wished I'd been born 20 years sooner.
I used that experience to land a job as a bench tech for an electronics mfr (when there was such a thing in America), for whom I worked for 8 years. I now work in network design for a Fortune 500 company.