[Boatanchors] AC/DC Series Filament Voltage Values

[Bill Stewart]

I am rebuilding a 1950 vintage 10 tube AC/DC superhet and have the series fil. sting hooked up and tested. I found some fil. voltage differences which brought up a couple of questions. There is a  46 ohm dropping resistor in series with the fil. string. (The schem. calls for a 42 ohm...only had a 46 ohm in stock). I have the tubes in the sockets with just the fil. wiring hooked up...no other wiring has been done.

Here is the lineup (also the sequence they are wired in the string) and fil. voltages w/115vac input:
*25L6GT     27.8vac
*25L6GT     23.6
6SG7         6.3
6SG7         6.5
6SB7Y       6.47
6SG7         7.04
6SF7          6.13
6SL7          6.43
6SL7          6.17
6H6            6.34 
*I swapped the two 25L6GT and the fil. voltages swapped also.

 As can be seen a couple voltages are off nominal (25 or 6.3 vac)...the 25L6GTs, one high and one low.
 One 6SG7 is 7.04 vac while other tubes may be right on or vary only a few tenths.
1. Is there a general tolerence on fil. voltages on these type of tubes? Is any tube damage likely to those with the  higher fil. voltages...guess that would depend on the tol. Seems I read in 1920's QST's that low fil. voltage could also damage a tube...not sure about my memory or if that would apply to more modern tubes.
2. Is there a way to equilize the voltages on the higher voltage tubes without disturbing fil. voltages down stream.
3. Am I looking for a perfect world, which doesn't exist in this situation?

That does it for now...I'm sure I'll be asking more as the project continues. Many thanks for any help.
73 de Bill K4JYS