"Avery Comarow" wrote in message
...
On Feb 13, 10:41 pm, "Richard Knoppow"
wrote:
At some time in the recent past there was a discussion
in this or the antique radio group about coil dope. As a
result I tried making some. ...What I did was to dissolve
polyfoam shipping material
in a mixture of MEK and xylol. I chose these two solvents
because both were listed on the lable of some old
commercial
coil dope.

Richard Knoppow

Proportions, please?

Mostly MEK. I added a little Xylol (AKA Xylene) because
I thought I saw it listed in an MSDS for coil dope. However,
the MSDS for the General Cement product lists only MEK
although the thinner is Toluene. If I do it again I will use
straight MEK. I added the styrofoam until the stuff got to
what seems to be the right consistency, about like honey.
Mine came out a sort of gray color rather than clear but the
pictures of the General Cement Q-Dope also look gray. My
styrofoam was scraps of shipping material from something I
mail ordered. It is amazing how quickly it dissolves, at
least at first. I used a small, wide-mouth, bottle I got
years ago. I would test the cap of any container you plan to
use with a little MEK to make sure it will not be attacked.
MEK is a rather wide spectrum solvent which will dissolve
latex and a number of other substances.
I will make some measurements when I have a little time
to see if my dope affects coil Q. Commercial dope has very
little effect.
MEK is available at any paint or hardware store and
styrofoam abounds. One can use styrofoam cups but I think a
sufficient supply can be found free.
I tried making my own after working on an old
Hewlett-Packard signal generator (606-A) where the high band
coils must be fastened down with it after adjustment. I
found none of my usual local suppliers had the stuff. I have
since found that Action Electronics, in Anaheim CA carries
it but that is a 30 mile drive from here. So, I decided to
make my own.



--
Richard Knoppow
Los Angeles
WB6KBL