Voyager electronics aren't as finicky as ours, but still ahead of Apollo. It is a good middle ground in terms of bus design. No fuel cells, just the RTG.
This is about as far as you can take solar power:
Heck, even the Sojouner mini-rover had a little something called a Warm Electronics Box with plutonium: http://marsrover.nasa.gov/technology...ironments.html
Because it had a solar panel up top, greens didn't notice, as was the case when Kaku stirred up a lot of anti-Cassini crap.