[Hallicrafters] Receiver question

[mac]

Tom,

The 6J5 grid and cathode are being used as a diode to rectify the  
output from the HF oscillator so as to provide a fixed negative bias  
on an AGC buss feeding  the mixer stage (only).  (The plate of the 6J5  
has no function in the circuit.)  Can't tell just what function or  
beneft this arrangement might provide.  Some other strange stuff in  
this set too like a second AGC line connected only to the IF amp, and  
feeding the HF osc. signal into the plate circuit of the mixer stage  
(apparently) as well as the grid.

Dennis D.  W7QHO
Glendale, CA

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On Nov 8, 2011, at 3:43 PM, Tom Lewis wrote:

> I know this is a Hallicrafters forum but maybe some one on here  
> knows the answer to this question.
>
>
> This summer I purchased a Silvertone 7038 receiver at an antique  
> ship in PA.  I down loaded the schematic from http://www.nostalgiaair.org 
> .  There is a 6J5GT Bias control tube. The plate and cathode are  
> both connected to ground. The grid is connected to the AVC voltage  
> thru a voltage divider. I checked the connections in the radio,  
> thinking the schematic had an error but it doesn't. The radio plays  
> fine (After recaping it) with or with out the tube. I checked  
> voltage with and with out the tube and it seems to do nothing. Am I  
> missing something here? What does the tube do?