[R-390] Weak BFO Cured

[Alan Victor]

Hi Dave. I think its all about gm, transconductance. The higher the value
the better and the transistor is typically 40,000 micro-mho/mA. Most small
signal tubes will not be nearly as large. Large FETs may also do well. The
J310 or a pair in parallel.

73' Alan

On Mon, May 6, 2019 at 9:06 AM David Wise <David_Wise at phoenix.com> wrote:

> I did not try other tube types.
> It's not gain in the sense we're used to thinking about, it's output
> impedance when operating as a cathode follower.  A tube with lower
> impedance is likely to work, for the same reason as my mod.
> This doesn't come out clearly in the spec sheets.
> Unfortunately, 6BZ6, 6CB6, 6DC6, and 6DE6 are disqualified because pins 2
> and 7 are reversed.  (6JK6 and 6EW6 are also disqualified by heater
> current.)
>
> Dave Wise
> ________________________________________
> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> on
> behalf of Perry Sandeen via R-390 <r-390 at mailman.qth.net>
> Sent: Sunday, May 05, 2019 3:42 PM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] Weak BFO Cured
>
> Yo Bubba Dudes!.
> Dave Wise wrote:   Some years ago my BFO gradually weakened and died.
> Replacing the tubedid not help.
> OK, question.  Did you try one with higher gain i.e. 6BZ6, 6JK6 etc?
>
> If not, do you think that it would have solved the problem?
> Regards,
> Perrier
>
>
>
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