[Boatanchors] Analyzing changes to Vacuum Tube circuits

[Ian]

...and get a good tube manual and learn how to draw a load line and see the
effect on the output as load and voltage is changed.  It's not all that
different from doing the same with a discrete transistor when trying to
figure out how changes will affect things.

Ian, K6SDE

> >>-----Original Message-----
> >>From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-
> >>bounces at mailman.qth.net] On Behalf Of Kenneth D. Grimm, K4XL
> >>Sent: Thursday, December 07, 2006 11:40 AM
> >>To: boatanchors at mailman.qth.net
> >>Subject: Re: [Boatanchors] A moment, a day, a passing of a generation/a
largequestion
> >>
> >>jeff wrote:
> >>>
> >>> Short of figuring out that old time machine quandary, how does one
learn
> >>> hollow-state practical tips?  Yes, I've read a few books, taken a few
> >>> things apart, attempted to build other things... but how does one
learn
> >>> without a nun over your shoulder, slapping your knuckles with a ruler?
> >>>
> >>> How does one learn to look at a circuit and make changes to alter the
> >>> output?  In a tiny class-A 6BQ5 audio amplifier circuit, if I lower
the
> >>> B+, will I lower output while retaining most of the fidelity?  I know
I
> >>> can use a resistor to lower the B+ - where do I start?  How much can I
> >>> lower the B+?  Or should I keep the B+ as-is for the other tubes and
> >>> just lower it for the output?  A 10w resistor in the power supply gets
> >>> hotter than anything I've felt in a radio, yet calculations show it
only
> >>> dissipating 2w - why is that?
> >>>
> >>> Where does one learn this stuff?  The practical info doesn't seem to
> >>> appear in the books.  Is it just slogging through, blowing stuff up,
and
> >>> conversing with virtual elmers?
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>Certainly, you can get lots of good input on design questions on the
> >>reflectors.  Another good source of advice is on the Usenet Newsgroup
> >>called rec.radio.amateur.homebrew .  One of the best series of articles
> >>that QST has ever run, in my opinion, is the one called Hands-On-Radio
> >>by Ward Silver, N0AX.  Ward writes in a style and at a level that
> >>non-engineers find accessible.  The articles are written as
> >>"Experiments" and Ward makes sure that you don't destroy what you are
> >>playing with and learning from.  If you are an ARRL member, you have
> >>access to all of these articles (48 of them and still going) at
> >>http://www.arrl.org/tis/info/HTML/Hands-On-Radio  If you are not a
> >>member, I can only say that just to have access to these Experiments is
> >>worth the price of a subscription.  Since everything at ARRL seems to
> >>turn into a book, one could reasonably expect the Hands-On-Radio series
> >>to be published in that form at some point in the future.
> >>73,
> >>
> >>--
> >>
> >>Ken K4XL
> >>k4xl at arrl.net