[Johnson] Re: [Boatanchors] Johnson-Viking 122 VFO Freq. Jump

[Brian Clarke]

He fellas,

To add to what Larry has said but to counter Sherrill's comments:

The conductivity of silver oxide is almost the same as that of pure silver. If an 
apparently silver contact has gone high resistance, it's more likely to be silver 
sulphide - direct result of incomplete combustion of the rotten gasoline foisted on 
us - or deposition of lead compounds - same source. Lead oxides and sulphates 
are good insulators. [Now that legislators have effectively removed lead from 
gasoline, the motor fuel manufacturers have increased the sulphur content - 
hence why many of our cars smell of rotten eggs - also very poisonous.] These 
resistive layers can occur without any contact arcing - but arcing will accelerate 
oxidation, not only of the parent metal but also of any other metal deposited 
there from the air. Larry's bond paper, or any acid-free paper will work wonders.
[Acid-free paper? ask an archivist in a library.]

The better devices used platinum for the points and flexible braid around the 
bearings - only seen on British and Australian military keys; please correct me.
It's very hard to deposit anything on platinum or to form its oxides, even at 
1000 C, say 1800 F.

73 de Brian, VK2GCE.
  Larry said:

  One of the things i used to use at work was a piece of bond paper placed
  between the contacts, push the contacts together and then pull the bond
  paper from between them.  No filing, no spraying, etc. etc.  In the case
  of pivot points, dunno!

  Larry
  W0OGH


  Sherrill Watkins wrote:
  > 
  > Gentlemen: On any key that is old it would be normal for oxidation to occur
  > on any piviot or contact. The keys made back in the 1940's and earlier may
  > especially be prone to oxidation of the points because silver was used and it
  > is prone to oxidation. Cleaning the contacts without removing the silver is a
  > problem. A friend has a circa 1925 Vibroplex and the contact points are so
  > oxidized that no current will flow through an ohmmeter. I suspect the
  > contacts are silver and he is reluctant to try to clean them. Some of the
  > older bugs had a little jumper wire around the piviot points because of the
  > tendency of oxidation to occur in the pivots. I think some of the WW2, J-36
  > bugs were made like that. That may have been part of the requirement of the
  > J-36 military specification? - 73- Sherrill W. k4own.