I have seen a lot of Saturns that had the bias turned way too high on the finals. Makes them run hot, and turns the metal tab black. As a rule, one final will croak first, cutting the power more or less in half. A flat-black layer of oxide on the metal-tab surface of a final transistor is a bad sign.
There is one capacitor between the final collector choke coil and the slug-tuned output coil. Older radios used a ceramic disc cap that would get hot and go bad. Some time in the early 90s they changed this to a silver-mica type. Can't remember the callout number on the schemo, but those are the two failures that come to mind.
Of course, you did align the transmitter stages upstream from the final, right? Just one tuning slug that's not peaked can do this as well.
73