[ARC5] Replacing the 12v tubes with 6volt types

[Kenneth G. Gordon]

On 18 Oct 2012 at 18:54, WA5CAB at cs.com wrote:

> I'm surprised, considering how long this sub-thread has continued,
> that no one has mentioned the obvious.  The first criteria for a 6
> volt tube to replace the 12A6 is that it draw the same filament
> current as a 6SR7, which is what it will be in series with.

Yes ! You are absolutely correct !

I had never thought of that because the only receivers I have ever seen with 
6 volt tubes in them had the filaments wired in parallel.
  
> 6SR7     300 mA
> 6C5       300 mA

    6J5       300 mA

> 6F6       700 mA
> 6K6       400 mA
> 6L6       900 mA
> 6V6       450mA
> 6W6      1200 mA
> 
> There are several later double-letter octal beam tetrodes and power
> pentodes but they all have heater currents of 450 mA or more.
> 
> Maybe that's why A.R.C. apparently plugged a 6C5 into a receiver,
> presumably to get a quickey 14 volt receiver for some reason.  :-)

And it works, too. A fellow member of this list told me that he used a 6J5 in 
place of the 12A6. He said that the change wasn't noticable until you wanted 
to crank up the audio to max. Then it would distort a bit.

Your analysis is very good, Robert. Why didn't the rest of us think of it? :-)

Ken W7EKB