[ARC5] BC-230 / -430 "Four Pin Tube Bases" Not Needed.

[Mike Hanz]

On 10/13/2014 10:49 AM, J Mcvey via ARC5 wrote:
> I like the idea of non-destructive "souping up" of these transmitters.
> In an effort to understand the retrofit I looked up the 6aq6 tube chart.
> I see that it has a plate resistance of 57K, whereas the the VT25 (10) has a plate resistance of around 5K.
> The 6sn7 and 12au7 have plate resistances around 7K . Couldn't you increase the power by running these triodes in parallel?

You are looking at the wrong specification.   Beam tetrodes don't often 
have published triode-connected specs, but that is what you should be 
looking for.  Not surprisingly, they end up with a plate resistance of 
the same order as normal triodes.  See Radiotron Designers Handbook 4th 
Edition for a discussion on the subject.

AB5S covered his tube selection and consideration process in previous 
posts, which are on the arc5 mailman website and bear reading to 
understand the retrofit, especially power handling ability.  Also of 
possible interest is a discussion of several aspects of triode connected 
beam tubes at http://oestex.com/tubes/triode.htm

- Mike  KC4TOS