RE [R-390] Nuvistaplug?

[Steve Hobensack]

  I've tried other tubes. I always go back to the 6dc6. It's resistant to 
overload especially on strong nearby stations. The nuvistor mod would work 
great for an r-390/sp-600 more or less dedicated to 14 mhz and above. A 
nuvistor would make a great 10 meter receiver. I use a 6dc6 in my sp-600 
also. Just have to touch up the rf slug.
....Steve...N8YE

Message: 1
Date: Thu, 22 Dec 2005 21:21:08 -0500
From: Mark Huss <mhuss1 at bellatlantic.net>
Subject: [R-390] Nuvistaplug?
To: R-390 at mailman.qth.net
Message-ID: <43AB5F14.4030506 at bellatlantic.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Here is one for all the experts.  A plug-in modification for SP-600's
was the Nuvistaplug.  This was a replacement for the first RF amplifier
in SP-600 that substituted a pair of 6DS4's in a cascode circuit.  The
resulting 6 to 9 dB increase in Signal to Noise level made the SP-600
sound like a new receiver.  My brother recalls that there was a similar
modification using a 6CW4 for the R-390A, popular with MARS operators.
I happened across the schematic today, and it looks like with changing
one pin in the Nuvistaplug, you could drop in the replacement for the
6DC6.  This should increase the signal to noise level of the first RF
Amp.  So has anybody even heard of this being attempted?