I have been using a MFJ-989C tuner for about (5) years without any problems.
Just recently I have noticed that on the higher band, 24 MHz that the SWR
occasionally would jump from an adjusted 1:1 SWR to infinity. A slight
adjustment of the roller inductance appeared to solve the problem although I
haven't ruled out a balum or antenna problem. I plan on investigating that
this weekend, however, before I open the cabinet and look for problems I
would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

I still have some old cleaning solutions from the old TV tuner days, some
electrical cleaner (Appears heavy duty stuff) but maybe there is some other
solutions someone might recommend.

Your thoughts and recommendations are appreciated

Ron - W4LDE

Ron,
Sounds like a dirty contact. Your cleaner should work.
So will soap and water, or 'Windex'. Just be sure to 'blow'
the dust out of it and dry it out.
'Doc

PS - In extreme cases, take it to the car wash (no wax).

On Wed, 22 Oct 2003 12:43:20 GMT, "Ronald Walters"
wrote:

I would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

Hi Ron,

One contact cleaner that I used that was better than most was
Cramolin. This is a monomolecular layer solution that you would use
very sparingly. However, as your tuner did not arrive brand-new (or
brand-used) with it, your problem may be more mundane.

The simplest way to defeat corrosion is with pressure. The spring
tension of the roller may have slackened up over the years.

73's
Richard Clark, KB7QHC

"Ronald Walters" wrote in message om...
I have been using a MFJ-989C tuner for about (5) years without any problems.
Just recently I have noticed that on the higher band, 24 MHz that the SWR
occasionally would jump from an adjusted 1:1 SWR to infinity. A slight
adjustment of the roller inductance appeared to solve the problem although I
haven't ruled out a balum or antenna problem. I plan on investigating that
this weekend, however, before I open the cabinet and look for problems I
would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

I still have some old cleaning solutions from the old TV tuner days, some
electrical cleaner (Appears heavy duty stuff) but maybe there is some other
solutions someone might recommend.

Your thoughts and recommendations are appreciated

Ron - W4LDE

I use Muriatic acid for this and when working on coax e.t.c
Inexpensive to purchase at hardware or lumber yards ( $4 a gallon)
I dilute it with an equal amount of water. This is also ideal
to clean copper prior to soldering
Cheers
Art

First came across this many years ago when I was in the Carribean on
one of many many business trips.
A local gave me a large sea shell with a beutiful pattern on it but it
was encrusted with all sorts of sea matter. Immersing it a short while
as per above
and all the crud was removed leaving a very shiny and elaborate
surface.
Ten years on the side board and still looks good and shiny. Passed on
the tip
to a vendor on the beach in San Juan so hopefully his business
improved.

Richard Clark wrote in message . ..
On Wed, 22 Oct 2003 12:43:20 GMT, "Ronald Walters"
wrote:

I would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

Hi Ron,

One contact cleaner that I used that was better than most was
Cramolin. This is a monomolecular layer solution that you would use
very sparingly. However, as your tuner did not arrive brand-new (or
brand-used) with it, your problem may be more mundane.

The simplest way to defeat corrosion is with pressure.

Garbage
For continued use you must have a wipe or what is termed a
scrubbing action. Period. Even with silver or gold the lack
of scrubbing action will permit intermitent contact unless
the power is high enough to blow away the oxides.
Art





The spring
tension of the roller may have slackened up over the years.

73's
Richard Clark, KB7QHC

On Wed, 22 Oct 2003 12:43:20 GMT, "Ronald Walters"
wrote:

I have been using a MFJ-989C tuner for about (5) years without any problems.
Just recently I have noticed that on the higher band, 24 MHz that the SWR
occasionally would jump from an adjusted 1:1 SWR to infinity.

According to the downloadable manual, page 3, the roller inductor has
a self-resonance killer that is switched in and out of the circuit
automatically, and you may feel a slight bump when it happens. That
may be causing your swr jump. The manual says not to be alarmed.

My roller inductor has some black, moist stuff on it. I just assumed
it was lubricant and haven't tried to remove it.

My tuner, about 10 years old, seems to tune my dipole just fine on
multiple bands.

Bob
k5qwg

A slight
adjustment of the roller inductance appeared to solve the problem although I
haven't ruled out a balum or antenna problem. I plan on investigating that
this weekend, however, before I open the cabinet and look for problems I
would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

I still have some old cleaning solutions from the old TV tuner days, some
electrical cleaner (Appears heavy duty stuff) but maybe there is some other
solutions someone might recommend.

Your thoughts and recommendations are appreciated

Ron - W4LDE

On 22 Oct 2003 15:05:58 -0700, (Art Unwin KB9MZ)
wrote:

Richard Clark wrote in message . ..
On Wed, 22 Oct 2003 12:43:20 GMT, "Ronald Walters"
wrote:

I would ask the group for recommendations on cleaning the roller assembly and
inductor to ensure good conductivity after I am done.

Hi Ron,

One contact cleaner that I used that was better than most was
Cramolin. This is a monomolecular layer solution that you would use
very sparingly. However, as your tuner did not arrive brand-new (or
brand-used) with it, your problem may be more mundane.

The simplest way to defeat corrosion is with pressure.

Garbage
For continued use you must have a wipe or what is termed a
scrubbing action. Period. Even with silver or gold the lack
of scrubbing action will permit intermitent contact unless
the power is high enough to blow away the oxides.
Art
The spring
tension of the roller may have slackened up over the years.

73's
Richard Clark, KB7QHC

Hi Art,

You are out of your turf. Pressure is the way all contacts work to
break the insulating barrier formed by oxides. Your typical abuse of
language here with "wipe" is another example that demonstrates
pressure. The indiscriminate use of chemicals to treat a mechanical
problem is one that I have demonstrated as being wholly unnecessary:
none of your new gear, nor any old gear just acquired that works fine
came with this chemical bath treatment.

Long before anyone here was born, precision contacts were tapered
plugs that fit into tapered sockets. The sockets were bifurcated
(split in two halves) such that the plug created the closure between
them with a simple insert and twist to break the layer of oxide.
Note, there is no "wipe" as the twist translates the torque into
pressure (wiping has nowhere to deposit what is "wiped" away in the
tapered socket). No one needed sandpaper or a bottle of acid to erode
the surface and corrode other parts through the solvent's vapor (a
very insidious imposition). There is a very good reason why
electronics manufacturers avoid acid core solder (unless they use a
water wash down following board construction and faithfully use rosin
core solder for touch up work - with extreme care not to mix the two
solders).

For contacts that have little pressure, the voltage presented across
them can penetrate the barrier; however, there are applications where
those voltages are not sufficient, and when the contact pressure is
not enough either, you get into these problems. Mechanical TV tuners
back in the early days suffered this problem and a special grease
surfactant was used to insulate the contact face from corrosion while
the pressure was sufficient to displace it for electrical contact.

73's
Richard Clark, KB7QHC

It's an "abuse of language" shared by many, including manufacturers of
switches and relays of all kinds. A google search on "contact 'wiping
action'" brought around 3000 hits. The few I glanced at dealt with just
that topic, using those words.

The only contact-related document I have readily at hand is a 3M catalog
of "Electronic Interconnection Systems". Just about every connector has
a specification for "wipe area" or "wiping area".

Roy Lewallen, W7EL

Richard Clark wrote:

Hi Art,

You are out of your turf. Pressure is the way all contacts work to
break the insulating barrier formed by oxides. Your typical abuse of
language here with "wipe" is another example that demonstrates
pressure. The indiscriminate use of chemicals to treat a mechanical
problem is one that I have demonstrated as being wholly unnecessary:
none of your new gear, nor any old gear just acquired that works fine
came with this chemical bath treatment.

Long before anyone here was born, precision contacts were tapered
plugs that fit into tapered sockets. The sockets were bifurcated
(split in two halves) such that the plug created the closure between
them with a simple insert and twist to break the layer of oxide.
Note, there is no "wipe" as the twist translates the torque into
pressure (wiping has nowhere to deposit what is "wiped" away in the
tapered socket). No one needed sandpaper or a bottle of acid to erode
the surface and corrode other parts through the solvent's vapor (a
very insidious imposition). There is a very good reason why
electronics manufacturers avoid acid core solder (unless they use a
water wash down following board construction and faithfully use rosin
core solder for touch up work - with extreme care not to mix the two
solders).

For contacts that have little pressure, the voltage presented across
them can penetrate the barrier; however, there are applications where
those voltages are not sufficient, and when the contact pressure is
not enough either, you get into these problems. Mechanical TV tuners
back in the early days suffered this problem and a special grease
surfactant was used to insulate the contact face from corrosion while
the pressure was sufficient to displace it for electrical contact.

73's
Richard Clark, KB7QHC

On Thu, 23 Oct 2003 10:40:36 -0700, Roy Lewallen
wrote:

It's an "abuse of language" shared by many, including manufacturers of
switches and relays of all kinds. A google search on "contact 'wiping
action'" brought around 3000 hits. The few I glanced at dealt with just
that topic, using those words.

The only contact-related document I have readily at hand is a 3M catalog
of "Electronic Interconnection Systems". Just about every connector has
a specification for "wipe area" or "wiping area".

Roy Lewallen, W7EL


Hi Roy,

And does that render the issue of pressure as "garbage" or negate any
comment offered by myself? Does it elevate the injudicious
application of chemicals? Does it replace common sense? Many of the
mythical lurkers might be lead down the primrose path of dunking their
'tronics into a vat of Coca Cola simply because of its Phosphoric Acid
content.

Is a google search the barometer of accuracy for
rec.radio.amateur.chemistry when supported by 3000 hits? If so,
"tits" would eclipse the charts. ;-)

73's
Richard Clark, KB7QHC

It's an "abuse of language" shared by many, including manufacturers of
switches and relays of all kinds.

==============================

Yet you still insist on using manufacturers' sales blurbs and specifications
as engineering educational standards.