I have a complete collection of EIMAC application notes. Unfortunately the QST
author doesn't specifically reference any one of them.
However, FWIW I recognize what the author is referring to...the "grid strapped
to ground" on the 3-500Z is how all the schematics of cathode-driven 3-500Z
amps in the application notes (and the tube data sheet) are drawn. I don't
recall ever seeing resistor or R-C circuits between grid and ground *from
Eimac*, but I could be mistaken. I'll need to browse through them tonight to
verify that.
Second, the parallel L-C input network is frequently shown in the EIMAC notes.
But only in conditions where the cathode input impedance is close to 50 ohms
(like 2x 3-500z or a single 3-1000z).
--
Scott Townley NX7U
Gilbert, AZ DM43di
---- Phil Clements <philc@texascellnet.com> wrote:
>
> Subject: Re: [Amps] QST
>
> Also, note that when the vox relay pulls in, you are now running at zero
> bias. Not too swift an idea for Z tubes.
>
> In addition to the two aforementioned guffaws, I have spotted several more.
>
> Maybe we should have a contest to see who spots the most errors in the
> article??
>
> The author refers to two Eimac technical bulletins that recommend direct
> strapping of all the grid pins to chassis, and using a simple L/C to chassis
> for the tuned input. Is there a web site where these bulletins can be
> downloaded? This would solve two reoccurring hot topics that show up here,
> and on other reflectors from time to time. (if such bulletins exist!)
>
> (((73)))
> Phil Clements, K5PC
>
>
> Bill, in that same article, the bandswitch of the SB-221 (pi net output
> section) had a floating rotor connection -- the bandswitch as shown wouldn't
> do anything. I remember spotting that when I glanced at the article and
> started chuckling...
>
> WB2WIK/6
>
> -----Original Message-----
> From: Bill Fuqua [mailto:wlfuqu00@uky.edu]
> Sent: Monday, December 18, 2006 8:43 AM
> To: AMPS
> Subject: [Amps] QST
>
>
>
> I am becoming more and more disgusted with the lack of technical
> knowledge QST authors. A fine example is the article about reviving old
> linear amplifiers in the most recent QST. There is a schematic and
> description of a half-wave voltage doubler which is claimed to have been
> used on many older amplifiers. But, everyone that I have seen uses
> full-wave voltage doublers. The only half-wave voltage doublers I have seen
> are usually in TV sets and other tube equipment that operated off the power
> line with out a transformer.
>
> 73
> Bill wa4lav
>
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