[Collins] Product detector for 75A-2 and 75A-3 Receivers

[Jim Brannigan]

About 30 years ago I bought a 75A3 as my primary station receiver.  I was
still in College and it was cheap.
I soon realized that it was a good AM receiver but I wanted to use it for
SSB and CW.
Reviewing the literature of the 50's and 60's I built several versions of
the "Universal Product Detector" for the NBFM socket....not bad, but there
were other problems....I changed mixers, RF tubes, bias, AGC.....
It was still an AM radio......and I sold it.....
Not to be deterred, I tried the same thing with an R-390A.  Even with a
CV-591 SSB converter, it is still an AM radio.
There was a good reason for Collins to develop the 75A4 and 75S series.

Remember what they say about silk purses and sows ears......

Jim

> Hi Folks,
>     I, abt 5 yrs ago, found some info on this subjected Prod. Det. on the
> web, at a site: http://military radio.com /(etc.) which no longer exists.
> I did make a paper cc of the installation/operating instructions &
> schematic, which match Glen's good memory.  If anyone would like, I can
> scan them & send via email.
>     Also there was an article in Nov. 1960 CQ mag entitled "Modifying The
> 75A-3 Receiver for Improved SSB Reception."  I have that mag also.  Plus,
> when I got my 75A-3 almost 7 yrs ago, from an old friend of mine, it had
> the needed plug-in turret socket for building the Prod. Det.   I don't
> remember now if the mag came too.  The rcvr had belonged to the
> father-in-law of my friend, who I had also known, so there's provenance to
> the rcvr for me.  I havne't built the unit yet, but will someday when I
> get a round tuit.
>     I also have a note, "Feb. '78 HR, 51J- SSB", so maybe that's another
> article.
> 73,
> Al, W8UT