[R-390] R-390a AGC Issue/Observation

[wb5uom at hughes.net]

A 5749 is the military designation for a 6BA6 is it not?
I am keeping this thread as a reference for if/when I have this issue.

David/ WB5UOM

----- Original Message ----- 
From: "Roy Morgan" <k1lky at earthlink.net>
To: "ANTHONY CASORSO" <canthony15 at msn.com>
Cc: <r-390 at mailman.qth.net>
Sent: Tuesday, April 14, 2009 7:59 PM
Subject: Re: [R-390] R-390a AGC Issue/Observation


> 
> On Apr 14, 2009, at 8:46 PM, ANTHONY CASORSO wrote:
> 
> > Looks like it is fixed. The problem was a way too hot v508, AGC  
> > amplifier. The tube had a Gm of 4000 when the roll chart showed 2050.
> 
> Tony,
> 
> 'Glad you found it.  That tube is odd for sure.. is it a normal  
> brand?  Sometimes a control grid can get knocked out of position and  
> get too close to the cathode (I assume) and give you too-high gain.   
> Maybe you can sell it on that e-place, touting "RARE!   "R-390 tube  
> found to be very high in gain ... go for the best for your radio!"   
> "We've never seen one with such high gain!"  (Leave out that you hope  
> to never see one again.)
> heheh
> 
> Thanks for posting the AGC vs. RF input measurements. This gives an  
> indication of the variation we can expect.
> 
> Roy
> 
> 
> Roy Morgan
> k1lky at earthlink.net
> 529 Cobb St.
> Groton NY, 13073
> 
> 
> 
> 
> 
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