[R-390] Collins Mechanical Filters

[roy.morgan at nist.gov]

Quoting "Craig C. Heaton" <wd8kdg at worldnet.att.net>:
..here is a link to a little website I've put together. It tells how to open a
Collins Mechanical Filter for a R-390/A and includes photos.

Craig,

Thanks much for the website and phtotos on the mechanical filers.

It seems to me that your next steps are:
 
1) find the required number 39 wire
2) find out how to dissolve the "black material" that was applied to the
windings so you can: a) remove them  b) count them so as to rewind them with
the right number of turns.

I have a suggestion for 2):
Mix up some "de-gooper": one third each acetone, MEK, and acetic acid. This
stuff is bad for you, but you only need a little bit. Immerse the coil in it
for day or five and see what happens.  I have used this stuff in the past (back
in the 60's) to remove some epoxy potting compound on somne IBM logid modules.
It strips some component markings but you don't care about that. Likely it will
dissolve the black stuff. It may dissolve the coil form but it's worth a try.

I may have some number 39 wire but I'm in the middle of a major upheaval with
most of my Junque and Treasure gone to storage as I get ready to move to a new
and better place for radios, including my collection of R-39x sets. Soo.. I may
not be able to locate any of the fine wire I have.

I do have at least two 4kc filters here that have failed: it sounds like your
methods will come in handy. Thanks for posting them.

Roy
K1LKY

 

Roy Morgan
7130 Panorama Dr.
Derwood MD 20855