[Eliot Ness]

OK captain, your pair of 47's will (more than likely) be fine and last a long time.

But instead of everyone getting in a p$ssing contest let's use this as a learning experience.  I applaud Mike showing how to use tube data sheets to determine the max (recommended) value of the 1st filter cap.  Often folks will randomly jack up the value of that cap trying to eliminate hum, but if one looks at the data sheet they can see the max value they should typically use.  BUT, the 2nd capacitor is the one you can jack up the value on w/o damage to the tube.

The tube data sheet is also helpful when you aren't sure what the value of that capacitor should be, such as the label is not legible or some hack stuck in a ginormous filter cap at some point in time and the schematic is not available or capacitor values not labeled.

I like to have a couple hard copies of RCA's tube books around, but there are several that are available for download or you can just do a search for an individual data sheet for a specific tube. 

Thanks Mike, for introducing the value of the tube data sheet for collectors who might not have been aware of their usefulness.