[Milsurplus] Smart People: BC-9A Opinions Needed
David Stinson
arc5 at ix.netcom.com
Tue Jan 3 10:51:57 EST 2017
Good morning. There's precious little specific
information technical on the WWI-era BC-9A
(SCR-77A) battery-operated, portable CW set.
Some general descriptions but no
clearly-copied schematic.
https://goo.gl/photos/uVYek56Zoja1jqQq6
There is a schematic on the inside of the cover,
but mine was stained and missing a large part
of the center of the diagram. I have worked
with what I could find to re-create the diagram.
Please look at this photo. The re-created part
is in the green outline. It is close to the smeared,
obscure copies I've seen but not certain. Does
this circuit make sense to you?
https://goo.gl/photos/RCMKFHrZKZBHoeLc7
Next: I'm working on power supply solutions
(other than the obvious batteries.) I need to do
some RF bypassing in the supply lines and need
a point I can call "Ground" in this circuit.
This diagram- Red lines appear to me to be
what one would think of as "RF Ground," while
the 120 and 40 B- lines reference in green.
That puts B- above the "RF Ground" by
the filament bias, adding to the grid bias
on the tubes. Do you think my analysis of
the red line being the place I could think of
as "Ground" is sound?
https://goo.gl/photos/bucwyMuC12jdfWWT7
Thanks for your input and prosper in 2017.
73 DE Dave AB5S
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