[MrFixr55]

Hi Dale, 

I corrected my earlier post to make it clear that since Ron had specs for the transformer, to go with them instead of the specs that I gleaned from the RCA and Tung Sol documents.
Yes, I got it out of RC12, and a Tung Sol spec sheet (and they have different specs.  RCA wanted everyone to think that they invented every tube, but I believe that the 42 was invented by Sylvania (who manufactured tubes for Philco after they stopped using RCA.  I don't know who invented the 2A5 or which came first (Philco was an early advocate of using 6V tubes in AC sets, possibly because they used them in car radios.  RCA was still using 2.5V tubes in 1933 in their home AC sets.  

When looking up the 42, in RC12, the reader is directed to the 2A5.  Both RCA and Tung Sol claim that, other than base (in the case of the 6F6) or heater specs (in the case of the 2A5), all the other specs are the same.  It seems to me that in the 650, the tubes are" cathode biased".  In the method popular in the 1930s, the cathodes are at chassis ground potential, but an unregulated C- analog (for lack of a better term)is developed by having resistance between Chassis ground and the center tap on the power transformer HV Secondary.  The center tap of the interstage transformer secondary goes to the desired tap on this resistor.  This is the same as putting the resistors between cathode and B-. IMHO, fixed bias involves a separate rectifier on a separate winding, like many Fisher HiFis, Ampeg B-15 Guitar amps, the Heathkit WA 5 and WA6 Williamson amps of the 1050s, etc.

The specs I gave were for triodes in Class AB (it does not mention AB1 or AB2), cathode bias (self bias) as opposed to a fixed C- bias) but the listed B+ voltage is 350V.  Definitely use any published Philco specs.  I posted the RCA and Tung Sol specs before Ron R,or another posted the specs for the speaker and output transformer.

Terry, you are right about the sockets.  I have seen some rather gnarly PCBs on AA5 radios and definitely on TVs around the Hor Opt tube.  Hamilton could find some 6 pin sockets on ePay., some of them ceramic.  hopefully that is just dust. If taking a brush and dry cleaning the socket does not remove carbon, worst case, drill out the burned area, so long as it does not dislodge the pin. Replacing the socket is the better idea.