[Milsurplus] NOS ART-13

[sbjohnston at aol.com]

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://af4k-crystals.com/   
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