I am a bit of a purist
when it comes to radio restoration so normally I will do little more
than give a piece a good cleaning. If brass is corroded I will clean
it, but I avoid polishing to a high gloss because I believe it reduces
the character and value of the piece. In the case of the multiple tuner,
however, I chose to do a full restoration because this is a very rare
and unique piece and deserves to be seen as it was when it was new; a
very high quality scientific instrument and a large step forward in the
technology of wireless communication.
As you can see in the
photo on the left, there was a lot of work to do. While the set was
mechanically in good shape (except for a crack in one of the condenser
tops), the brass was somewhat pitted and corroded, and the black ebonite
components (the knobs, top, front, and condenser tops) had all turned
brown with age. In addition all three tuning condensers were frozen as
was the large, ganged tuning switch on the front.
I knew this was going
to be a very tedious and difficult job, but I was inspired by Jim
Kreuzer, probably the world's premier Marconi collector and expert, who
had his own tuner restored several years ago. Jim had engaged a master
craftsman named Art Albion for the task, and fortunately for me, Art
documented the entire process step by step in the June, 1987 issue of
Antique Radio Classified!
Using Art's article as
a guide, I began the systematic and tedious process of disassembly. Most
of the screws on the unit were frozen, and all of them used the very
thin screwdriver slots typical of early scientific gear. After several
days of alternating penetration oil with careful application of pressure
through my modified set of screwdrivers I was able to break free all of
the screws except one. Amazingly, despite eventual disassembly of the
set to it's smallest piece I was never able to get that one screw free!
Thankfully, it didn't prevent me from proceeding.
Once I had the top
open and all of the solder connections removed (that is a story all in
itself!) I was able to disassemble the unit. This is where Art's map
really helped. Without it I would never have figured out the trick to
removing those tuning condensers!
All of the brass was
soaked in a dilute muriatic acid solution and then cleaned with 0000
steel wool. The parts that needed more work were cleaned with 000 steel
wool or emery cloth prior to final polishing. Once the brass was clean
and polished it was covered with a thin coat of lacquer.
The tuning condensers
are made of zinc plates separated by a dielectric of thin rubber. The
zinc had corroded with age which made the unit impossible to turn. Each
condenser must have at least 40 of these sets of plates & rubber pads so
to clean each one individually would have taken me another 100
years! Instead, I built a jig made of brass rods attached to a wooden
base that mimicked the rotating action of the condenser. I slid the
plate/pad unit onto the jig and through constant rotating pressure and
liberal application of silicon spray was able to free up the condensers
again. (Note: apparently freezing condensers was a common problem
on the multiple tuner even when it was still in use, according to a 1917
text called " The Maintenance of Wireless Telegraph Apparatus".)
Once the brass and
condensers were completed I set myself to working on the ebonite
panels. I polished them using a small electric hand polisher with
automotive rubbing compound on a medium scotch-brite pad. This took
quite some time as I had to stop frequently to see if I had rubbed
enough to return the black finish but not so much as to remove the panel
etching. When the brown was gone, I did one last polish with a fine
polishing pad, cleaned and dried the panel, and then applied whiting to
the panel markings. I removed the excess whiting with 0000 steel wool,
gave it one final polish and was done.
There is lots more
detail of course, but I won't bore you with it all here. Leave it to
say that the unit was reassembled and the result is what you see above!