That really doesnt work very well as now there is no way to apply operating
or cutoff bias without more work than it is worth. Plus anything that
increases gain potentially reduces stability since neutralization was
marginal to start with on 10-15M.
By simply adding a .01 to .02 1000V disc cap across the existing 200pf grid
capacitors and replacing the parasitic suppressor resistors with Ohmite OY
series resistors (use the original coil or wind a new one) the results are
the same. High stability along with more output than is safe for Chinese
tube which are only rated at 125W dissipation and have poor emission life
when abused.
I also suggest no more than 75W drive unless a 10-12 Ohm non inductive NFB
resistor is used at the input.
At 600-650W out the amp will last a lot longer and the signal difference
wont even be heard.
Carl
KM1H
----- Original Message -----
From: "Jim W7RY" <w7ry@centurytel.net>
To: "Mike Baker" <k7dd@cox.net>; <amps@contesting.com>
Sent: Saturday, October 06, 2012 11:48 AM
Subject: Re: [Amps] Odd Problem with SB-201
The SB-200 is a great amplifier. BUT, the girds need to be directly
grounded. To do this, you need to completely re-wire the metering
circuits. I've done that when I add my QSK board. With the grids
grounded, it's more stable, puts out more power with less drive.
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