[ARC5] BC-375 Re-Tube Project- Scratch Three

[David Stinson]

Three candidate tubes for the  
"Cheap Tubes for the BC-375" project have disappointed.  
1625, 837 and 7984 will not "hold up" in this service.
Once the screen voltages are dropped to spec,
the tubes lack the gain to oscillate reliably, even 
with heavy "gimmick" cap coupling between grid
and plate in the OSC stage.

Running the screens above spec will make the tubes 
"sound" good- for a little while.  
Then the screens give it up.   The 837 is an exception.
It's screen is tough and it stood-up well to being 
directly connected to the plate.  
But even with heavy feedback, the 837 just won't
deliver "keyable" oscillation.  Starts too slow and 
yelps like a houng dog.

Not giving up.  There is an answer- just got to be persistant.
In the mean time, lowering the B+ to 500 Volts, adjusting the 
thermal compensation capacitor, properly adjusting the keying relay
and using a "clean" 211 in the MO have tamed the 375 on 
both 40 and 30 meters to at least "Classic Exchange" standards.

More work to be done.

73 DE Dave AB5S