[Boatanchors] Receiver Filter Adaptor- Diagram Correction
David Stinson
arc5 at ix.netcom.com
Fri Feb 19 05:49:59 EST 2016
Arden- All:
Sorry to take a while to reply. Work presses.
I made an error in the "in situ" diagram (Me? Make an ERROR?
Say it ain't so!). Here is the corrected V1 plate circuit
showing the in-rig screen bypass, C226B (a plate bypass when
using the adaptor), in the proper place (don't forget to hit
"reload" to clear the old diagram out of your browser cache):
http://home.netcom.com/~arc5/TCS/AdaptorInSitu1.jpg
Here are the original TCS IF stages for reference:
http://home.netcom.com/~arc5/TCS/TCSIF.jpg
R215 is the screen resistor which becomes a plate dropper when
using the adaptor. It's not what you would want in V1's plate
circuit, but "the rules of the road" say it is fixed and
immuteable, so must be accepted. Any substantial change in R215
and one could no longer replace the adaptor with the original
12SK7. Fortunately, the V1 stage seems to work well as-is and I
like that there are only 4 mils of current in that filter primary
winding. I may do some more fiddling to see if I can't get the
DC off the filter, shunt-feeding V1, but I risk running afoul of
the "Law of Pernicious Parts Count" and it's "Sam Rayburn
Corollary."
There do seem to be some issues with V2 at only 20 plate Volts.
I'm going to try the suggestion of one of our kind and "smart
people," bringing the plate back up to 120 volts and setting
stage gain with the cathode resistor. A question for our "smart
people" (assuming anyone is still reading at this point):
Should I bypass the new cathode resistor, or is there some
benefit from leaving some degeneration in there?
Happy weekend, everyone.
GL OM ES 73 DE Dave AB5S
P.S. I was asked why I was posting this to the "ARC-5" list since
it isn't an "ARC-5" receiver. I do because some people there
believe what we're discussing has applications in just about any
old receiver and they asked me to do so. "DEL" button works
great, guys ;-)
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