[Nick3092]

I would consider using 8.2 uF 630 V metallized polypropylene caps for the two filters right after the rectifier. These can handle much greater ripple current than modern electrolytics, and they will basically last forever. 

I have been using this type of cap for the first filter in several radios and they work great. They are about $6.50 each from AES and small enough to stuff inside the original electrolytic cans.

Hmm, I think I saw those once, and sort of balked at the price. Long lasting is a plus. I've never actually restuffed a can before, and given how big those are, I'd pretty much have to. There wouldn't be room under the chassis for that.

However, that takes me back to my 4uF/8uF question (where Philco dropped from 8uF to 4uF for the filter caps in run 5). I can't find a run number stamped on my chassis. But I can tell I at least have a run 6. In run 6 it says they moved the two 25k resistors from hanging directly off the interstage transformer to directly on the 6B4 sockets. Mine has this change made, so I think it's safe to assume mine is at least a run 6. However, along the way someone replaced the original filter cans, and threw in 2 non-Philco 8uF cans with wire leads. Not sure why they would have done that, assuming the originals were clearly marked 4uF. Unless they just looked at the schematic (and not the run changes), and figured someone else put in the wrong values, so they should put in the 8's.

What are the overall effects of changing the values of the filter cap values? All I know is that if you go higher, you might get better hum elimination, but you could raise B+ too much. And should I go with 8uF or 4uF?

Thanks!