I don't own a brown Princeton, but I offer to buy my friend's every time I play through it. Just an amazing-sounding amp that will make any guitar plugged into it sound good!
I could take a look at the filter cap can next time I see it if you're interested. I wonder if Fender had 30/30/30 cap cans in mind when designing the amp, but they subsequently got a good deal on 30/20/20 cap cans.
- Scott