tv: vertical jitters

When capacitors start to fail, the problem usually gradually improves as the set warms up. In this case I'd be more inclined to suspect solder joints or a semiconductor. A can of freeze spray might be helpful in diagnosing it.

The combination of jitter and washed out picture might suggest a bandwidth or gain problem in the IF circuitry, but the intermittent aspect of the symptoms you go on to describe suggest more likely failing of lead-free solder in the V-O/P stage, a re-work of the soldering in this area is probably the quickest and easiest thing to eliminate a possible cause. If that doesn't cure it, warming various areas of the panel with a hairdryer as already suggested might give a clue to capacitors with ESR problems, before I bought an ESR meter I had devised a variety of means to weed these out, in PSUs faulty caps often run hot while smaller caps in signal stages were often sensitive to gently twisting them on their leads. One very useful instrument I still keep handy is a Steinel continuity checker, it has an inverse parallel pair of LED, a battery and a thin film PTC thermistor so the test current starts briefly high and decays to a suitable value for one or the other of the high efficiency LEDs, With the suspect cap out of circuit, the tester would give a short flash as the cap charged - then if the button was released the other LED would flash as the cap discharged - caps with ESR problems caused the flash to visibly "ramp up" before decaying again.