[Milsurplus] contact cleaners

[WA5CAB@cs.com]

Brooke, George and group,

I'll second George's comments from fairly extensive and long term experience 
with vibrators.  Some ten years ago, I began to notice that vibrators packaged 
prior to VJ day and never opened and used since then had a near 100% 
probability of not working.  Within the past year or two, the same problem has started 
to show up in those packaged during the Korean War.  Used units that were in 
service into the Vietnam War period will usually still work the first time you 
apply power, regardless of their actual original vintage.  The only exception 
that I am aware of is the VB-16 used only in the PE-237.  Aside from physical 
size (it is the largerst vibrator that I have ever come across) and number of 
contacts, the significant difference between it and all of the others is that 
it does not have a sponge rubber sleeve around the mechanism inside the outer 
can or cover.  The culprit is sulpher from the sponge rubber.  After 40+ 
years, I can't recall which suplher compound it actually forms with the silver, 
but chemical cleaners don't help (and you have to open up the vibrator to apply 
them anyway).  The two fixes are either mechanical abrasion (contact 
burnishing tools, which also requires opening the crimped seal) or electrical 
punch-through.  I normally use the latter method.

In a message dated 10/3/2003 8:16:30 PM Central Daylight Time, 
gl4d21a@juno.com writes: 
> One of the misunderstood aspects of the contact problem is that it is
> rarely as simple as oxidation.  This is apparent when you consider the
> silver plating on many switches and connectors.  Silver oxide is a fair
> conductor, which is why it is chosen.  Other compounds of silver do not
> fare so well.  Gold is not supposed to corrode at all.  HA!  One of the
> principal offenders is sulfur, which migrates out of most old rubber
> products.  

73
Robert Downs - Houston
<http://www.wa5cab.com>
<wa5cab@cs.com>


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