Are these things I should consider bad

[Findm-Keepm]

Originally Posted by jr_tech

I have been looking at the schematic and scratching my head over that cap... what does it do? Is the transformer somehow set up to be a constant voltage device?
jr

That transformer supply is ferroresonant - an L-C tank, and causes the transformer to provide some level of regulation itself. If the 440V cap goes bad, you'd know it, with a dead set, or really low voltages. If you get B+ and other transformer secondary voltages, move on, as the ferroresonant circuit is working. Zenith stressed this after seeing a spike in folks ordering the cap. Reliability testing showed the cap had a 40+ year life, and shops that didn't understand the circuit would order and replace the cap to eliminate that as the cause of whatever problem they had. I've only seen one go bad- and a dead set was the result, with the blown input fuse as well.

We always kept the caps from the sets we junked, and I used one two summers ago as a makeshift run capacitor in my HVAC Gaspack to keep the AC going in July 2011. Date code on the cap is 1979....

Cheers,