[Milsurplus] contact cleaners; vibrator contacts

[WA5CAB@cs.com]

George,

Oops.  You're correct on the contact material.  Got it confused in my 
(getting old) mind as I've recently run into a batch of T-17 microphones with 
inoperative PTT switch contacts.

And the mass of cleaning or protective materials is of course why I wouldn't 
think that using any of them on vibrator contacts would be a good idea.

My original source for the external repair method did say 40 watt light bulbs 
(and only mentioned series-drive 4-pin vibrators), but I found early on that 
25 watt bulbs worked just as well 40's and have been using them for so long I 
had forgotten the original said 40's.  I've never tried to measure the 
efficiency of vibrators repaired in this way, partly because 90% of the time the 
power supply or radio that the vibrator was going into was hundreds of miles away 
and partly because the thought never occurred to me.

In a message dated 10/5/2003 6:56:38 AM Central Daylight Time, 
gl4d21a@juno.com writes: 
> According to Mr. Mallory, vibrator contacts are principally Tungsten.  I
> have never encountered an expert in Tungsten chemistry, but my experience
> with used vibrators is that the contacts have to be cleaned manually when
> they get that old.  Tungsten Sulfide (Sulfate?) appears to be a tough
> material.  I am very familiar with the 40 watt light bulb method, having
> learned that in the 50s, when we were already having the contamination
> problem with commercial vibrators in consumer car radios.  My further
> experience trying to optimize cleaned vibrators leads me to the
> conclusion that all the parameters involved in vibrator operation aren't
> fully covered in the books, as I have never been able to restore full
> performance to even a simple interrupter unit after the contacts have
> been accessed.  Timing is right, waveforms look like the design manual,
> but the efficiency is never as good.  So, I am not sure what the effect
> of adding a material with any viscosity to the contacts would be, as
> contact pressure and resistance are apparently extremely critical.  At
> least the silicone materials wouldn't carbonize as some of the old
> cleaners we used to use certainly did.
> 

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


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