[Milsurplus] LS-3 Description & Details

[WA5CAB at cs.com]

Groups,

I had several questions from list members since my posts this afternoon and 
thought since traffic is low tonight I'd save myself answering them again 
individually and some of you from needing to ask.

LS-3 was the standard loudspeaker used with medium and high power vehicular 
and shelter mounted sets during WW-II and on into Korea.  It is a 6" dia. 
permanent magnet loudspeaker with 8000:3.2 ohm matching transformer mounted in an 
8"x8"x4.75" felt lined steel box.  The box is intended for bulkhead (walls for 
you ground pounders) mounting or for sitting on benches, desks, etc.  For 
mounting, it has four tapped holes in the corners of the rear of the case.  All 
components are mounted on a louvered removable front panel.  

In the lower right corner of the front panel is a JK-33-A 7/32" dia. 
3-circuit jack (with flip-up cover) to mate with PL-68 (more commonly used with 
microphones).  For years I assumed that this was to keep marginally trained troops 
from plugging the wrong cable into it, but a list member recently pointed out 
that this was a carry-over from it's predecessor which had a field coil type 
speaker, requiring a bias supply.  The high side of the audio goes to the Tip 
contact (12 volts DC would be on the Ring).

WW-II production was mostly finished in black wrinkle.  Korean War production 
in black semi-gloss.  Post Korean War production in green semi-gloss.  The 
final production in the 60's was as LS-215/U, green semi-gloss finish and with a 
4000 and 500 ohm tap on the matching transformer.

So to connect up an LS-3, you need a two-conductor cord with a PL-68 on the 
LS-3 end and an appropriate connector on the other end.  For BC-312, 314, 342 
or 344 this can be another PL-68 (making cord CD-265, the original used) or 
PL-55 (into the Phones 2nd Audio jack) making cord CD-1117.  The latter also 
works with BC-224 or BC-348, BC-652, Hammarlund Super Pro's, R-388's, Command 
Sets, vehicular installations of GF/RU, etc.  In sets with Hi-Z and Lo-Z taps on 
the audio output transformer, be sure that they are connected for Hi Z.

Last time I checked, Fair Radio still had a fair (pun intended) stock of 
CD-307-A bailout cords and PL-68 or PJ-068 cutoffs.  Replacing the JK-26 or JJ-026 
with a PL-68 or PJ-068 makes a CD-1117 equivalent (you'll have to cut back 
the cord's outer jacket and Z-fold the black ground lead).

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at houston.rr.com> (Backup email)