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

[Roy Morgan]

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