On Thu, 4 Dec 2008, JIMMIE wrote:

Date: Thu, 4 Dec 2008 06:23:48 -0800 (PST)
From: JIMMIE
Newsgroups: rec.radio.amateur.homebrew
Subject: 6L6 substitute

After years of avoiding morse code I am finally getting into it. the
ideal of operating a very simple transmitter appeals to my junkbox/
trashcan construction mentality.
I am looking for a substitue for a 6L6 that has the plate brought out
the top. I was trying to build a little Glowbug transmitter but was
having all kinds of problems neutralizing the the thing. I think I
would have better luck if I can separate the grid and plate circuits
from each other.

Maybe you should look at how you bypassed the screen grid to ground with a
capacitor. Once I built a 6146 pentode, grounded-cathode amplifier for 160
meters and was disappointed that it went into self-oscillation. After
thinking about it, and then the light bulb over my head went off, I looked
and realized I did not have the screen grid bypassed to ground (what, 0.01
mfd or so?), and when I soldered one in, all of my self oscilation
stopped. You should not have to worry about neutralization if you are
anywhere in the HF bands (or, at the worst, maybe on ten meters).

I've built several 6AQ5, 6V6, etc., one tube, xtal-controlled
CW transmitters. All worked fine.

I am considering an 807 as a replacement Suggestions
would be appreciated.

You might also want to check the connections to the control grid. If for
some reason you have a -- for example -- cold solder joint and the control
grid is actually floating, then it will oscillate all by itself, too.

Jimmie