[AMRadio] Re: Old Firestone radio


D. Chester k4kyv at charter.net
Sat Aug 2 09:27:48 EDT 2008


> Replaced the 5Y3 rectifier and repaired the speaker.  Believe it or not, 
> the
> flexible wire from the cone connection of the voice coil was open.  Only 
> the
> string was left in the middle.  I was able to tack a piece of solder wick 
> to
> the top side of the voice coil wire and made a small hole in the cone then
> soldered the other end to the frame terminal.  I then glued the small hole
> on the cone.

Something that would work better than solder wick would be a  strand taken 
from a piece of copper wire rope.

I don't recall where I found it, but I have a piece a few feet long, 3/16" 
diameter.  It is made like aircraft cable but the metal is pure copper.  It 
is about as flexible as a piece of cotton rope.  It has 7 strands just like 
tower guy wire, but each strand is made up of dozens of extremely small 
gauge copper wires bundled together.

My large antenna changeover relay, which I acquired n.o.s. but was built in 
the mid-1930's according to an ad I saw in QST or RADIO, was in use for only 
a couple of months before the flexible wire lead attached to one of the 
moveable contacts broke.  I fixed it, using several strands taken from that 
wire rope and paralleled together.  Within a couple of weeks, the one on the 
other contact broke in a similar manner. Metal fatigue.

The wire rope repair has been in use for over 4 years now and is still 
intact.  I don't have a clue what that copper rope might have been used for 
originally, but it's worth its weight in gold for making flexible wire 
leads.

The copper wire in the speaker probably just wore in two from metal fatigue, 
like the supposedly flexible leads to my relay contacts.  The relay wire was 
nothing more than ordinary stranded copper wire.  No telling how many of 
those otherwise excellent changeover relays were tossed out because of that 
problem, which was due to poor design of the flexible leads to the contacts.

Don k4kyv 



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