[Milsurplus] AN/GRR-5 Power Supply Questions

[Neil Barnett]

>    4. C101, C110 and C111 are 1,200 mfd/15 WVDC caps used as filters.
> Can I use 2,200 mfd/50 WVDC? How about 1,000 mfd/50 WVDC?

I presume these are electrolytics, in a 12-13.8 VDC system.
Unlike ceramic and polyester capacitors, where it is permissible
(and even desirable) to use units of high voltage rating so as to
avoid breakdown of the dielectric, electrolytic capacitors must
not be run at less than about two-thirds of their rated working
voltage.

If you attempt to use 50 WVDC electrolytics in a 12-13.8 VDC
system, they will fail to attain their full rated capacitance during
operation, thus reducing their effectiveness as filter elements.
Additionally, I'm sure research has shown that such operation
leads in the long term to the total failure to form any capacitance,
i.e. a cumulative deterioration in the ability to "form" the correct
dielectric.

My advice is to forget the 50 WVDC units.  Try to find units of
the correct capacitance in the now-standard 16V rating (should
not be too difficult!).  Use more capacitance, rather than less, if
you can't get an exact match, for example 1,500 mfd/16 WVDC.

73 de Neil ZL1ANM