Fairly certain flyback transformers were also a continuing problem with the eMac too... but from what I can work out, yes most of the issues that plague those wretched things are to do with faulty analogue circuitry, not so much logic-board issues.

So yes, it'd stand to reason if this is the case, that if you were able to find a servicable analogue board and PSU then it'd probably work again. That said, actually finding secondhand items that are functional is a different story... eMacs get binned by the dozen all with similar issues. Even if you were to find working components or event a working machine, there is little to say they wont flake out too fairly shortly... If it's anything to go by, I have 4 or 5 1Ghz eMacs here that are all paperweights and all came from the same place. :-/

Short of determining the specific faulty components and replacing them with brand new ones, eMacs are basically all doomed to fail, and are one of those few machines I'll happily write off as a lost cause. It's a shame about the poor build and crap styling, as in concept they were a good idea.