[ARC5] Info sought about output transformer in BC-221-AK

[WA5CAB at cs.com]

Belay my last.  It has been maybe as much as 40 years since I last read the 
1944 edition of TM 11-300 through.  Since then, I've only gone to the 
appropriate chapter, usually to the schematic.  What I wrote originally agrees 
with the statements in Paragraph 10 - Headsets, which says that early models 
used Headsets P-18 or P-20 and later model use Headset HS-30 with Cord 
CD-605.  Which is the long Hi-Z cord.  What it fails to say is that that only 
applies up through BC-221-AE.  BC-221-AF through BC-221-AN use HS-30 and Cord 
CD-874, which is the long Lo-Z cord.  The reason for this is that up through 
BC-221-AE, the audio output is RC coupled.  From BC-221-F the audio output is 
transformer coupled.  Further confusion is caused by the list of components 
that make up each SCR-211- model.  All of the lists save one include both 
the CD-605 and the CD-874, with no note indicating when you should use which.

The 1944 edition has no proper parts lists, those having by that time 
mostly been moved to SIG 7, SIG 8, or SIG 7&8.  So you can't look up the specs on 
any of the parts, including the audio output transformer.  However, when 
all of the BC-221's except the -AN were built, each came with a digest size 
manual on only that one model.  I don't happen to have the small manual on the 
-AK, but I do have ones on about a third of the 27 models, including four 
of the six that came with the output transformer.  They all have proper parts 
lists.    Two say primary 5645 turns, secondary 747 turns, and the other 
two say primary 10,000 ohms, secondary 250 ohms.  So that's the full answer.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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