[ARC5] Silver refurbishment
Dennis Monticelli
dennis.monticelli at gmail.com
Fri Dec 25 00:36:02 EST 2020
Richard,
Thank you for educating us on sulfides vs oxides and performing those
conductance tests on substrates coated with DeOxit D5. That is consistent
with the claims of Caig Labs and of the many hams that have used the
product, including on transmitters. Dried D5 is not conductive either at
DC or for RF. My concern is the silver sulfide that it removes. If that
residue ends up on the substrate and is not washed away by the flushing
action of the D5 (a product that is only 5% active ingredient and the rest
carrier) or by some other means before it dries, there could be a
conductive path left behind.
All,
D5 is too weak to deal with darkened silver surfaces in my opinion. I have
cleaned many a wafer switch in both receivers and transmitters up to the KW
level. D100 is my product of choice for silver and other metals. This
100% concentration product will remove the dark sulfides. My technique is
to put a small amount on the tip of a cotton swab. I do not use drugstore
swabs which are loosely spun and leave cotton hairs that cling to the sharp
corners of contacts. I use the tightly spun industrial swabs on long
wooden stems made by MG Chemical. Less than $5 for 100. They come in
regular head size and narrow tapered. Both are very useful. The D100
reddened tips are used to scrub the wipers. You will have to hang up the
wafer position in between detents in order to reach some of those wiping
surfaces but the effort is worth it. The surfaces will come clean and some
of the DeOxit will then convey to the pincer contacts and act upon them
too. Rotate the switch, go back several times and clean until your swab is
no longer blackened. If you slip and the blackened tip places the dark
dissolved silver sulfide on the ceramic or phenolic areas in between
contacts then that area should be cleaned. This gets back to my concern of
the first paragraph.
Bonus Step: When you're done take a fresh swab and barely wet it with Caig
Labs G100L. This tiny bottle cost a bloody fortune but lasts forever. It
will inhibit the formation of future sulfides and oxides on precious metal
surfaces. I am looking at the antenna coil on an ARC-5 right now and it is
as bright as the day I originally cleaned it ten years ago. I had used
silver cream with a toothbrush, lots of soap & rinsing and finally a light
coating of G100L. In my shack I have many silver plated Amphenol coax
connectors. Over the same period of time these have lightly tarnished so I
know the preservative is doing its job.
Dennis AE6C
On Thu, Dec 24, 2020 at 3:54 PM Richard Knoppow <1oldlens1 at ix.netcom.com>
wrote:
> FWIW, I tested Deoxit-5 for conductive residue. I used an
> unused Bakelite terminal strip. I measured the leakage of the
> path between terminals in two ways: one was a General Radio
> Megohm meter, the other was the ohm meter function of a
> Hewlett-Packard 410B. Both measure very high values of resistance
> but the GR meter does it with 600 volts applied while the 410B
> does it with some very small voltage.
> I got the same results with both; no leakage after treating
> with the Deoxit. I measured before and after treatment. The
> measured resistance was very low and remained the same. The
> conclusion is that Deoxit does not leave a conductive residue.
> As far as ceramic insulators go, if this is not glazed
> insulation it might absorb something from the silver residue. I
> did not have any samples to test but my thought is that the
> surfaces should be rinsed off thoroughly soon after treatment
> since anything absorbed might be bound to the grain of the
> insulation.
> Also, to be clear, silver oxidizes with great difficulty. The
> material found on silver plated surfaces is nearly always silver
> sulfide, a poor conductor. Silver oxide _is_ formed in
> photographic emulsions by the action of peroxides in the
> atmosphere but the conditions there are special and unlike those
> applying to surfaces like plated coils or contacts. Ironically,
> the main way to prevent the silver in photographs from becoming
> oxidized is to treat them to form silver sulfide. Silver sulfide
> is extremely stable and a small amount prevents further sulfiding
> or oxidation. Its too bad its a lousy conductor.
> Two methods of cleaning can be found on the web. The first is
> an electrolytic method using aluminum foil and baking soda. The
> silver object is immersed in a solution of baking soda in hot
> water with a sheet of aluminum foil. The aluminum will absorb the
> sulfur from the silver.
> Another method is to use a reducing agent such as oxalic acid
> or phosphoric acid, which will combine with the silver sulfide
> and leave behind metallic silver. Both are primary ingredients in
> several commercial cleaners such as Naval Jelly, Zud and
> Barkeeper's Friend. Both of the latter are rather abrasive. I
> think Tarn-X also uses one of these acids but have not looked it
> up. Also (by memory) citric acid is a reducing agent and is found
> in lemon juice. Lemon juice and salt make a good cleaner.
> My experience is that Tarn-X and Naval Jelly are too powerful
> and tend to remove some metallic silver from plated surfaces.
> If any are used they should be rinsed off.
> I have not seen any comments about using the electrolytic
> method on switches but it works like a charm on silver plated
> connectors.
>
> On 12/24/2020 7:46 AM, Dennis Monticelli wrote:
> > I would like to reiterate that regardless of what chemical you
> > use it's important to not allow the dissolved silver to soak
> > into the ceramic substrate material, particularly if you're
> > dealing with close-spaced wafer switch contacts. If that
> > happens , rinse it out. Alcohol is one way to do it. Flooding
> > the area with DeOxit D5 is another way. If the part can be
> > removed you can use soap, a toothbrush and lots of water.
> >
> > Bottom line is not to leave conductive paths.
> >
> > Dennis AE6C
> >
> > On Thu, Dec 24, 2020 at 7:07 AM Glenn Little WB4UIV
> > <glennmaillist at bellsouth.net
> > <mailto:glennmaillist at bellsouth.net>> wrote:
> >
> > If anyone is interested, I have an interesting, but clearly
> > off topic,
> > story about silver sulfide and electronics.
> >
> > 73
> > Glenn
> > WB4UIV
> >
> > On 12/23/2020 10:58 PM, Richard Knoppow wrote:
> > > The problem is that its not silver oxide, its silver
> > sulfide, which is
> > > a very poor conductor. There are various substances which
> > will either
> > > remove it but you will be removing some metal too. Any
> > silver polish
> > > will do the trick but its best to start with something mild.
> > >
> > > On 12/23/2020 6:12 PM, Brooke Clarke via ARC5 wrote:
> > >> Hi Ken:
> > >>
> > >> It's my understanding that Silver oxide is an excellent
> > conductor, so
> > >> other than cleaning there's not much to do.
> > >> --
> > >> Have Fun,
> > >>
> > >> Brooke Clarke
> > >> https://www.PRC68.com <https://www.PRC68.com>
> > >> http://www.end2partygovernment.com/2012Issues.html
> > <http://www.end2partygovernment.com/2012Issues.html>
> > >> axioms:
> > >> 1. The extent to which you can fix or improve something
> > will be
> > >> limited by how well you understand how it works.
> > >> 2. Everybody, with no exceptions, holds false beliefs.
> > >> -------- Original Message --------
> > >>> Dave Stinson at one time suggested using some product
> > to clean and
> > >>> refurbish the silver
> > >>> coils in our transmitters.
> > >>>
> > >>> I believe he also mentioned refurbishing the silver on
> > switch wafers
> > >>> and contacts....or
> > >>> someone here did anyway.
> > >>>
> > >>> So what did you use to remove the black oxididation
> > from such
> > >>> surfaces without damaging
> > >>> them?
> > >>>
> > >>> I have to clean some old bandswitches which are
> > oxidized. I will
> > >>> have to use Q-tips and some
> > >>> care to do this, but I need the "stuff" mentioned here.
> > >>>
> > >>> Ken W7EKB
> > >>>
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> > >>
> > >>
> > >>
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> > --
> >
> -----------------------------------------------------------------------
> > Glenn Little ARRL Technical Specialist
> > QCWA LM 28417
> > Amateur Callsign: WB4UIV wb4uiv at arrl.net
> > <mailto:wb4uiv at arrl.net> AMSAT LM 2178
> > QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE
> > ARRL TAPR
> > "It is not the class of license that the Amateur holds but
> > the class
> > of the Amateur that holds the license"
> >
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> --
> Richard Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
>
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