[Milsurplus] NOS ART-13

[Bob Camp]

Hi

Ok, the “rest of the story” …..

They ran into an issue making crystals in WWII. Basically the solution was to change the manufacturing process to include (more) etching in ammonium bifluoride. The etch process reduced issues from debris left over from the grinding process. 

The same basic issue continued to come up at various times and in various plants for at least the next 5 decades …. ( = the “solution” was not a perfect fix ….).

Fun !!!!

Bob

> On Aug 7, 2024, at 5:47 PM, sbjohnston--- via Milsurplus <milsurplus at mailman.qth.net> wrote:
> 
> True - it is sometimes possible to bring vintage FT-243s back to vigorous life by careful disassembly and cleaning.  Sometimes distilled water and a paper towel is enough if dirt is the only problem, but I've found that if the contamination issue was at play a solvent like denatured alcohol or mineral spirits and a toothbrush were needed.  
> 
> I recall reading that during the work on crystal "aging" during WWII, troubled crystals after a few months/years were observed microscopically to have rubber and other deposited materials laying in the scratches/grooves on the quartz left by the grinding/lapping process.  One of the suggestions was to end the manufacturing with an acid etch final frequency adjustment.  This left a smoother surface and did not seem to "catch" the contamination and avoid the slow down of the crystal.
> 
> 
> Steve WD8DAS  
> 
> sbjohnston at aol.com  
> http://www.wd8das.net/   <http://www.wd8das.net/>
> http://af4k-crystals.com <http://af4k-crystals.com/>/  
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