[Heath] SB-200 - more info

[Wilson Lamb]

Sure sounds like some VHF oscillations are going on.
Does it ever make noise in your HT, scanner, etc.??

WL
----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: <Heath at puck.nether.net>
Sent: Thursday, January 19, 2012 3:32 PM
Subject: [Heath] SB-200 - more info


> Another result of my installing the KM1H parasitic chokes is that the 
> tubes no longer turn red
> after only a few minutes of steady 14 WPM CW, as they did previously, and 
> output remains
> at 550 watts with my present well-worn Chinese tubes.
>
> I am very pleased, but am proceeding with other modifications.
>
> My purpose and goal is to arrive at a completely and unconditionally 
> stable amp which will
> NOT be dependent on tube type or manufacturer.
>
> My next step will be to remove that connection to the "unused" pin on the 
> right-hand tube
> socket which is used as a tie-point for the grid input connections.
>
> I have suspected for some time that, due, probably, to the inernal 
> construction of the tubes,
> this connection is causing some sort of unwanted feedback.
>
> I base this suspicion on the fact that the RIGHT tube of a matched-pair is 
> always the first one
> to get red if the amp is driven with a CW signal to full-output and the 
> key is held down until
> red plates start to appear.
>
> I have already "balanced" both the filament bypassing, and the ALC 
> connections, both of
> which are, to my mind, severely unbalanced in the original configuration.
>
> Doing so, although much more aethestically pleasing to me, did not change 
> the "red on the
> right" issue much.
>
> More later.
>
> vy 73,
>
> Ken W7EKB
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