[Collins] Re: Blue bakelite connector for Collins radios

[Dr. Gerald N. Johnson, electrical engineer]

I've dug back as far as my catalog collection goes. I don't find the
blue 78S11 socket or 86CP11 plug offered in blue as a distributor item.
I did find the socket offered in one Amphenol catalog in steatite and
both in some others in black phenolic or mica filled phenolic (probably
a tan or brown color).

The American Phenolic Company that became Amphenol did use a blue
diallyl phthalate in many of their fancier and mil spec connectors. This
old catalog says that material met MIL-P-4389 and MIL-P-14D. This
catalog was from 1961.

I presume that Amphenol based their connector business on their own
molding plant and tooling so they could use any handy material for a
special order that would run into the molds or that could be forced into
the molds.

At least 20 years ago, I used a black phenolic connector on the cable
from my home brew supply connected to my 32S-1 and its not failed yet.
The other end of the cable uses a 6 pin 300 series Jones plug, not rated
for the high voltage. My high voltage may be a slightly lower than the
unloaded 516F-2.

I very much doubt the blue plug and jack exist in Collins stock or
anywhere but in the equipment and cables that were built with it.

My 32S-#A manual dated 1975 lists the plug as 86CP11-1008, vendor
Amphenol, CPN 372-1950-000. My older 32S-1 manual lists it as having
phenolic insulation with CPN 372-1757-00. Diallyl phthalate isn't
phenolic.

If I broke the center guide pin, I'd be inclined (both for color and
insulation quality and especially for my laziness) to machine a
fiberglass rod to fit the hollow guide pin and remains of the plug as a
brace (maybe even steel but I'd prefer the fiberglass for its insulating
properties) and use some really good epoxy to reassemble the plug. And
that way save replacing all those heavy heater circuit wire and all
those bypass capacitors.

With different dielectric materials for the different colors, its
possible that the voltage ratings are different, but if the blue plug is
also phenolic, the voltage difference probably isn't significant. The
mica filled phenolic should have had the least RF loss and maybe the
best voltage performance, though the difference between the dielectric
constants of the phenolic and the mica may actually lower the working
voltage rating because of voltage concentration in the lower dielectric
constant material. Though the voltage limits are probably most
pronounced as surface leakage, not bulk dielectric leakage, the leakage
made greater by moist dirt.

And if I remember correctly the 5R4 socket in the typical 516F-2 is the
black phenolic socket and has a bit higher voltage applied than the
power connector, though those have been known to fail from high voltage.

I know where there is a small supply of black phenolic plugs and jacks,
but I've never seen blue outside of a Collins radio.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.