[R-390] Hammarlund SP-600 IF output versions and mods

[Al Parker]

(I thought this went to the list ystdy, but didn't)

hi Charles, et al,
     I don't presently have a late model (after ~s/n 17,000) which has 
factory disc ceramics and/or the ver. 3 IF output.
     I do have an SP-600-JX-28, which is an even later (apparently) 
version, with disc ceramics, and a different method of construction.  It 
uses many terminal boards rather than much point to point wiring, and 
also has a different manner of developing AVC voltage.  That makes the 
take-off of the IF signal to the IF output jack a bit different, maybe 
Version 4 (or V.5, as the SP-600 VLF is different yet, I think).
     The JX-28 takes the IF signal for AVC before the BFO, so the BFO 
can be used with AVC.
     Mine -28 is presently not giving as much AVC voltage as it should, 
in my opinion, and I haven't figured just why yet.  There were only 100 
of these made, so not a lot of heads can get together to figure out 
glitches.
     I've att. a .pdf file for Charles with the diagram(s), if anyone 
else would like it, let me know directly.
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 5/2/2013 9:41 AM, Charles P. Steinmetz wrote:
 > I'd be interested in hearing from folks who have SP-600s with the third
 > version of the IF output.  In my experience these are very rare, but I
 > may have seen a skewed population of SP-600s.  My working hypothesis is
 > that these radios also came from the factory with disk ceramic bypass
 > capacitors (again, a very rare, late-production variant).  Data from
 > more units would help to validate or invalidate the hypothesis.
 >
 > Thanks,
 >
 > Charles
 >
 >
 >
 >> As you requested, please find attached three partial schematics of the
 >> Hammarlund SP-600 showing different versions of the IF output circuit
 >> and a 2008 post from the R390 mailing list discussing the problem with
 >> two of the versions, how to tell which version one has, and what to do
 >> to correct radios with the problem.
 >>
 >> Please do not post these or circulate them further.  Thank you.
 >>
 >> Enjoy,
 >>
 >> Charles
 >
 >
 >
 >
 >