[Johnson] [Collins] Help 75A4

[Al Parker]

Hi,
    It's not uncommon, e.g. SP-600 meters have the same trouble.  Low 
current, low voltage, not enough oomph (technical term there) to clean the 
contacts.  As said, gold (non-corrosive) plating is the thing, but most 
didn't spend the $.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

"there is nothing -absolutely nothing- half as much worth doing as simply 
messing about in boats."
   Ratty, to Mole


----- Original Message ----- 
From: <TELEGRAPHER at att.net>
To: <gzook at yahoo.com>
Cc: <Boatanchors at mailman.qth.net>; <Johnson at mailman.qth.net>
Sent: Tuesday, February 03, 2009 11:24 PM
Subject: Re: [Johnson] [Collins] Help 75A4


>
> I wonder if the Johnson people had the same problem.  The meter switch on 
> my viking II has to be played with continuously to get meter readings. 
> And that one would be a big bear of a job to replace.
>
> Larry
> W0OGH
>
>
>  -------------- Original message from Glen Zook 
> <gzook at yahoo.com>: --------------
>
> Tarnish on silver contacts is not silver oxide but is silver sulfide.  It 
> occurs gradually due to exposure to the atmosphere where minute amounts of 
> various sulfur compounds naturally occur.  According to the Silver 
> Institute tarnishing on electrical contacts has negligible effect on the 
> conductivity.  This was
>> based on over 20 years of experimenting and field observation.
>> Now there are definitely other things that build up on switch contacts 
>> which require removal ("cleaning").  These include dust, nicotine, and 
>> all sorts of pollutants.  Also, over time it is certainly possible for 
>> contacts to lose
>> tension and therefore do not make positive contact.
>> However, the fact that the silver plating on the contacts tarnish is not 
>> cause for concern.  But, cleaning of the switch is definitely a good idea 
>> to remove
>> the other pollutants that can cause intermittent operation.
>>
>> Glen, K9STH
>>
>> Website:  http://k9sth.com
>>
>>
>> --- On Mon, 2/2/09, Dr. Gerald N. Johnson  wrote:
>>
>> Likely the switch has silver contacts. They oxidize and won't conduct low
>> voltages unless the oxide is broken down with higher voltage, like a 
>> volt. I had
>> that in my 51J-3. I replaced the switch with on having precious metal 
>> (gold is
>> good) contacts. No more problem.
>>
>> Or it could be a bad solder connection in the S-meter circuit between the 
>> switch
>> and the tube.
>>
>>
>>
>> ______________________________________________________________
>> Collins mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/collins
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Collins at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>


--------------------------------------------------------------------------------


I wonder if the Johnson people had the same problem.  The meter switch on my 
viking II has to be played with continuously to get meter readings.  And 
that one would be a big bear of a job to replace.

Larry
W0OGH



  -------------- Original message from Glen Zook 
<gzook at yahoo.com>: -------------- 

  Tarnish on silver contacts is not silver oxide but is silver sulfide. It 
occurs gradually due to exposure to the atmosphere where minute amounts of 
various sulfur compounds naturally occur. According to the Silver Institute 
tarnishing on electrical contacts has negligible effect on the conductivity. 
This was
  > based on over 20 years of experimenting and field observation.
  > Now there are definitely other things that build up on switch contacts 
which require removal ("cleaning"). These include dust, nicotine, and all 
sorts of pollutants. Also, over time it is certainly possible for contacts 
to lose
  > tension and therefore do not make positive contact.
  > However, the fact that the silver plating on the contacts tarnish is not 
cause for concern. But, cleaning of the switch is definitely a good idea to 
remove
  > the other pollutants that can cause intermittent operation.
  >
  > Glen, K9STH
  >
  > Website: http://k9sth.com
  >
  >
  > --- On Mon, 2/2/09, Dr. Gerald N. Johnson wrote:
  >
  > Likely the switch has silver contacts. They oxidize and won't conduct 
low
  > voltages unless the oxide is broken down with higher voltage, like a 
volt. I had
  > that in my 51J-3. I replaced the switch with on having precious metal 
(gold is
  > good) contacts. No more problem.
  >
  > Or it could be a bad solder connection in the S-meter circuit between 
the switch
  > and the tube.
  >
  >
  >
  > ______________________________________________________________
  > Collins mailing list
  > Home: http://mailman.qth.net/mailman/listinfo/collins
  > Help: http://mailman.qth.net/mmfaq.htm
  > Post: mailto:Collins at mailman.qth.net
  >
  > This list hosted by: http://www.qsl.net
  > Please help support this email list: http://www.qsl.net/donate.html


--------------------------------------------------------------------------------


> ______________________________________________________________
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> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Johnson at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html