[Boatanchors] Charles Smith works on the R-390A. A lot!

[Bill Meara]

 I got into this only because when I tried to buy on e-bay just the VFO tuning capacitor for and HT-37, the seller sent me the entire VFO stage (all except the tube).  This was going into a homebrew solid state SSB transceiver.  So naturally I thought about how to substitute an FET for the tube.  It was really easy.  I just soldered some tube socket pins on the J310 and plugged them into the appropriate places on the tube socket.  I had to take two of the plate dropping resistors out of the circuit, but that was it.  It seems to be working great.  No need to built a high voltage supply for this thing.  So here I think the solid-stating makes sense. 
Charles Smith KV4JT is not extremist on this, He writes "I am not suggesting you do this to a museum piece or collectors model but it certainly would be a good idea for the abused and ratty ones that have been sitting in attics and garages for decades and look like something that needs to be thrown out.  It is a good way to resurrect them and preserve them for many years to come."  
Dale:  Please tell us how the therapy goes.  I feel your pain OM.  73  Bill     On Sunday, August 21, 2022 at 04:47:28 PM EDT, McDonald, J Douglas <jdmcdona at illinois.edu> wrote:  
 
  #yiv4420877248 P {margin-top:0;margin-bottom:0;}But .. I think of all possible boatanchors, the R390A is the ideal candidate for 
a very serious effort to do a solid state conversion with superb performance.
Why?
Simple: the mechanics. 

These allow LC tuned circuits at every conversion that track, for goodspurious rejection. But getting the RF and conversion stages to work 
as well as tubes would be hard because input impedances of the 
transformers are all wrong. 

And then there's the (necessary) agc. Not easy. 

Doug McDonald


From: boatanchors-bounces at mailman.qth.net <boatanchors-bounces at mailman.qth.net> on behalf of Bill Meara via Boatanchors <boatanchors at mailman.qth.net>
Sent: Saturday, August 20, 2022 5:42 AM
To: Boatanchors List <boatanchors at mailman.qth.net>
Subject: [Boatanchors] Charles Smith works on the R-390A. A lot! This may be too much for some of you, but I found it really interesting: 
https://urldefense.com/v3/__https://soldersmoke.blogspot.com/2022/08/trigger-warning-solid-stating-old-tube.html__;!!DZ3fjg!_4jBJKFFME7A8FDNcwiYmpRp6s-FMG0XHFsrHDQB_-mtioQB5PyukjXJoDRkna7cDBMiLgGmmlV-Yacl80m76vuJSsuVCg$ 

73  Bill N2CQR
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