[R-390] switch contact cleaning question

[Barry Hauser]

Dave!

 Don't do it!  TarnX is very harsh stuff with sulphur (dioxide?) content.
It
is said to take some of the plating with the oxide.  There may not be much
plating left where the contacts rub on the rotors to begin with.

 Lately, I haven't had a single rx come in here that wasn't partially deaf
due to oxidized switches, particularly the bandswitch.  However, with a good
deal of patience, DeOxit will work.  It would probably work faster if I
broke down and bought the liquid form in the very small and pricey bottle.
It's supposed to be concentrated, so they tell me.

What I do is take a wood swab, remove some of the cotton, saturate it with
DeOxit from the nozzle of the spray can and re-twirl the cotton so it
doesn't get caught in the works.  Then wet the rotors and contacts and work
the switch back and forth through it's travel.  If you can see the
rotor(s) -- the metal disk that runs through the clip contacts -- then
rotate the switch so you can reach a section and rub the swab on it.  Keep
re-wetting the swab because the DeOxit evaporates quickly.

It will look like nothing is happening on the blackened rotors and contacts.
Forget about making the outside surfaces of the contacts shiny -- doesn't
count anyway.  You should notice the black coming off on the swab, even
though the switch rotor is still black.  It is also not necessary to remove
all the black oxide, but after several passes you'll see some shiney metal.
The main thing is to cut through the oxide with the swab and switch to the
point where you can see a shiney fine line through it around the rotor
metal.  Sometimes, after the swab has had it, I break the end off at an
angle and use it as a burnishing tool -- scrubbing the rotors with the stick
soaked in more DeOxit.  Not abrasive enough to do any damage, but be careful
not to slip and bend the contacts.

 Go easy on the DeOxit on the switch wafers -- don't spray them if you can
help it.  Probably posted this a dozen times by now, but DeOxit can swell up
 the phenolic and that may cause close-fitting rotors to bind.  Probably not
a big deal on a single or two-wafer switch, but could be bad news on a
bandswitch.  Frankly though, there have been times when I let fly with the
stuff.  Recently I had an SP-600 turret and RF strip that refused to work on
all bands until I blasted it.  Then there are some switch arrangements with
wafers so close that you can't get in there with a swab.  Also, leave the
rotors wet, come back a while later and do it again. Sometimes with DeOxit
I've found that it works after a wait and things suddenly brighten up.

Forget about TarnX.  They also say that anything cleaned with it oxidizes
much quicker -- and worse -- aftewards.  You just have to thin the oxide
down enough so the contacts can wipe down to the metal.  Last treatment with
DeOxit should leave the stuff wet and allow to air dry as the cleaner leaves
a protective residue.

Hope this helps

 Barry



>
> ----- Original Message -----
> From: "Dave Metz" <metzd@intelos.net>
> To: <r-390@qth.net>
> Sent: Wednesday, December 26, 2001 10:14 PM
> Subject: [R-390] switch contact cleaning question
>
>
> > I'm sure this has been posted a few times but I cannot find a reference.
I
> > am working on an R220 that looks something like the R390A but is  closer
> to
> > a shipanchor at 40 plus tubes!. Anyway, I am looking for some
suggestions
> > as to how to clean a badly oxidized wafer switch---it's black! I have
> > sprayed deoxit on it to no avail. It sort of looks like I need something
> > that has the ability to cut through tarnished silver. Fortunately, the
> > switch is able to be pushed back and brought out into the open. Now, I
> need
> > to put something on a q-tip, but what is the mystery. I'm thinking of
> > tarnex but am a bit gunshy till I check with the wisdom of this group of
> > experts.  In advance, thanks for any pointers.
> >
> > 73's
> > dave
> >
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>