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[AMPS] Vac Variable Mounting

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Subject: [AMPS] Vac Variable Mounting
From: (Rich Measures)
Date: Fri, 22 Jan 1999 03:35:51 -0000

>Looking for some wisdom...  Need to mount a couple of Jennings CVCJ type
>vacuum variables and have never seen a close-up view of the proper way to
>physically mount them.  

?  Vacuum variable capacitor plates are made of soft copper.  The plates 
are so soft that they are affected by gravity.  At the Jennings factory, 
vacuum capacitors are connected to an oscillator/frequency counter, and 
rotated horizontally to evaluate plate concentricity. . If the plates are 
concentric, the frequency of the oscillator will not change as the 
capacitor is rotated .  If it is necessary to align the plates, the 
device under test is discretely bumped on a cushion and retested.     In 
their catalogue, Jennings says the best way to mount vac. variables is 
vertically.  This quite obviously takes a right-angle drive and a drive 
shaft to the turns-counter on the front panel. / (Groth turns counters 
are ideally suited for this arrangement. -  Multronics/Cardwell makes an 
ideal right-angle drive that replaces the collet on the end of the 
vacuum-variable tuning shaft). / .  .  Vertical mounting uses less 
chassis space than horizontal mounting.  However, vertical mtg. typically 
requires a 4 to 5 inch deep chassis.    On the other hand, for a tetrode 
with handles, a deeper chassis makes the job of finding a suitable 
filament-transformer easier.    //  free, unsolicited advice:.  Test all 
vacuum components on a high-pot before installation.  I have seen new, 
out of the factory carton, vacuum variable capacigors that had been in 
storage for a few years, which had partially lost their vacuums due to a 
defect in the seals.  

-  later, Bill


R. L. Measures, 805-386-3734, AG6K,  

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