[Collins] 51J parts

[Dr. Gerald N. Johnson]

On Wed, 2008-04-16 at 10:57 -0500, Ed Wirtz wrote:
> hi,
> 
> I'm looking for RF coil L105 assembly for a 51J-3 or 4. The one I have is so badly burned that the coil form disintegrated. The coil is in the 8-15 MHz range.
> 
> Thanks in advance for any help and 73,
> 
> Ed, KØBKA

I've been doing some digging. I downloaded the military R-388 manual and
it has more details, but not enough to allow making the coil without
digging into my receiver to see the details which I am NOT going to do.
Its all buttoned up and in a rack.

The R-388 manual says L105, L108, and L112 are the same. 20 turns #28
enamel on a phenolic form 0.295" OD and 2" long. Signal Corps stock
number 3C1084S-45. Collins part number (from a 51J3 manual) 504-3061-001
I don't know if the coil is close wound or spaced. It says the slug is
0.256" OD though I wonder if that shouldn't be 0.250" OD. That is a THIN
wall coil form. Not quite 0.020" thick. Were I to try to make one, I'd
probably start with 5/16" fiberglass rod (if I didn't find something of
those dimensions in my shoebox of coil and coil forms) drilling it in
the lathe to clear the slug. Then I'd mount that tube on an expandable
mandrill and turn down the outside to dimension and wind the coil and
glue it fast with GC coil dope. I'd hope to be able to use the original
terminal rings, though I might have to use rings from some J.W. Miller
coil forms. Since a considerable number of the coils in my shoebox came
from Collins surplus store, there is a very slight chance of there being
some tubing already made or even the coil itself (though not identified
by part number).

The fiberglass rod might have been intended as a tomato stake or a
bicycle flag staff.

-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer