What to do on used sets?

[Eric H]

It really depends on the set, stuff from the 80's will likely need nothing unless they use knobs, then they might need some cleaning and lube.

Some 70's sets like the Zenith CCII need to have the safety caps checked so you don't blow the tripler and CRT, and of course that era will need Pots and tuners cleaned.

Preventive recapping is always an option, particularly in the sweep circuits where the most problems occur. You can prevent a Vertical IC or a HO Transistor from getting destroyed with some fresh caps.

90's and up just watch them till they die then toss em.