[R-390] “A” Tube Filament Voltage

[Perry Sandeen]

GM List,

There has been considerable discussion on the list regarding tube shield efficacy and filament voltage.

There has been mention of running the tubes filament voltages at 95% of the nominal rating of 6.3 volts.  Thus 6.3 times .95 equals 5.995 volts.  On all six of my R390A power transformers the filament voltage is stated as 6.1 volts not the 6.3 that at least I had ASSUMED.  

This contradicts the Y3K manual chapter 5 values which are given as 6.3 volts.  I am TDY for several months so I haven’t been able to make any measurements.

Now comes the question: Is this the actual voltage or a typo?

If 6.1 volts is the actual value then I guess that the Collins engineers realized that there would be heat issues affecting tube life and used this value to help prolong tube life..

Could some one enlighten the list on the true value?

Regards, Perrier