Good ol' Howard W. I can remember tricks like putting a tomato paste can over a tube to make it heat up faster and maybe show an intermittent problem. Blasting things (not tubes!) with the freon dusters would sometimes show intermittents, too.
Originally Posted by henry finley
I had a Zenith console with a maddening problem in the convergence circuits, the bottom convergence would change intermittently between good and way off, I traced it to a coil on the convergence board...after about 5 hours.