[Boatanchors] Reducing filament voltage

[mac]

David,

Let me be the first to recommend a series resistor.

The only 6.3 volt tube I find with the same base connections is the  
6A4 which has similar but somewhat lower element voltage and current  
ratings.


Dennis D. W7QHO
Glendale, CA

****************

On Apr 16, 2011, at 1:55 PM, David Knepper wrote:

> I am finishing the wiring on my Collins 4A (circa. 1934) transmitter.
>
> The problem is to produce 2.5 volts for the 47 volt oscillator  
> tube.  The
> newer transformer that I am using has a 6.3 volt winding.  Someone  
> told me
> about using a couple of 1N4007 in series from the filament lead to  
> the pin
> socket.
>
> I am sure that somone will tell me to use a series resistor or use a  
> later
> tube with a 6 volt filament.  What tube might that be to replace the  
> 47
> tube?
>
> Any ideas?
>
> Thank you
> David Knepper, W3CRA/W3ST
> Editor of the Collins Journal
> Secretary of the Collins Radio Association
> www.collinsra.com
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