[Milsurplus] AN/GRR-5 Power Supply Questions

[W7QHO at aol.com]

This thread raises some interesting questions that sent me back to various 
handbooks, Terman and the Internet.

In my design work as an EE and a ham over a 50 year period I must confess 
that I never paid too much attenuation to the finer technical points concerning 
the application of electrolytic capacitors.  The common rule of thumb was to 
allow a margin of safety, i.e., use a 450 working volt unit in a 300 - 350 
circuit.    Paid attention to polarity, of course, and didn't use this type in 
timing, RF, etc., applications.  Was surprised to hear about the ARRL Handbook 
admonition about running units "well below" their deigned working voltage.  
Checked several editions besides the years cited by Neil and found the warning to 
be consistent but the consequences of doing so are never spelled out.  The 1956 
IT&T "Reference Data For Radio Engineers" warns against "extensive" voltage 
derating of electrolytics and notes that a 450 volt unit operated at 300 volts 
will eventually become a 300 volt unit.  This could be what the ARRL is 
talking about.  Am sure I have used 450 volt units in 250 volt or less applications, 
especially in ham work over the years but don't recall any problems 
encountered  in doing this.

As George, W5VPQ has pointed out, "The chemistry of electrolytics has 
undergone several radical transformations in addition to the ongoing product 
improvements."  Cornell Dubilier now says electrolytics may be used at voltages lower 
that their ratings, see below which also gives a great rundown on how these 
units are manufactured and other information.

http://electrochem.cwru.edu/ed/encycl/misc/c04-appguide.pdf

Dennis D. W7QHO
Glendale, CA