[Milsurplus] 28-8S Mystery

[Robert Downs]

Charlie, et al

Here's the story.  The engineers at Hallicrafters before the War who were
designing the HT-12 that eventually became the BC-669-A decided that they
needed a connector about the size and number of pins as the AN 310n-28-8x
but they decided that they needed five #12 contacts instead of two.  So, as
they did or had done several other times before and since, American Phenolic
(later Amphenol) modified the inserts so that pins A, B and C took #12
contacts instead of the original #16.  The modified connector was
re-designated as AN 310n-28-767x (where "n" is a digit that designates the
metal shell type and "x" is P or S, for gender.  And the modified connector
has 7 #16 and 5 #12 contacts.  "PF" has nothing to do with the modification.
P means Pin and F means Fixed (non-rotating) contacts, which was an option.
Unfortunately, the -8 is molded into the inserts so they just left it.  Some
later production has the correct numbers stamped on the nose of the cable
connectors and the square flange of the chassis connectors.  But I haven't
seen but a few examples.

The standard 28-8 connectors may still be in production, but the 28-767
hasn't been made since the Korean War..  It is possible, assuming that you
have extra pins or sockets, to modify a 28-8 to a 28-767 but the depth of
the holes for the females is critical.  And if the source connector was a PF
or an SF, the contacts in the modified contact holes will not be fixed.

On the $95 for one new connector, most of you guys are 'way out of date on
military circular connector prices.  $95 is probably at the high end of the
going price new for a circular connector without rear insert contacts of
about the 28 shell size these days.  So my guess is that he looked up the
recent new price of an AN 3108-28-8S or P (not knowing that the one that he
has isn't that) and quoted the book price.  When I have them, I've been
getting $35 for the cable connectors (same as for U-7/U and U-9/U) and $25
each for the chassis ones.

Happy New Year to everyone!


Robert Downs


-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of CL in NC via
Milsurplus
Sent: Monday, December 30, 2019 19:05
To: Milsurplus
Subject: [Milsurplus] 28-8S Mystery

I have a BC669 and power supply waiting for me to restore it, something I
will start when I get caught up on a couple other things first.  So, while
it waits I have searched for the elusive Cannon 28-8S to mate with the rig.
The modern Amphenol 28-8S does not match the WW II layout.  Low and behold,
a 28-8P came up on Ebay, and the seller said he had the mating connector for
it.  He wants $95, ouch big time, but a close examination of his pic showed
it to be 95% correct.  There should have been 5 larger diameter pins laid
out like a pentagon in it, but it only had 3, it was missing the two on the
end of one row.  I looked at a picture of the other end that goes to the PS,
and it seems like it only has 3 large pins like the one he is selling, but
from the pic, it is hard to say, but somewhere along the line, my PS had
that connector swapped for an octal, so don't have one to compare to.  So,
now there are 3 iterations of this plug and socket. I wonder if the fact
that the writing on the male connector on the BC669 says 28-8 PF is
indicating a special type that is in the truly unobtanium category.  I have
run across another fellow who has been searching for 7 years trying to find
one with no luck.  Guess I will have to either change it out on the 669, or
using pins that fit and epoxy a home made connector body for it.

Charlie, W4MEC in NC