Filter cap selection

[Gary Pewitt]

Gang, while looking through the DigiKey catalog for caps
to use in repairing a couple of old receivers for a friend
(Atwater Kent 55C and Philco 40-180) I saw most of the caps
were rated for DC working voltage.  Since I don't know the
voltage ratings on the original caps I just picked 400v caps
as close to the original capacity rating as possible.  Usually
a bit higher if I couldn't get the exact value.  What concerns
me is the power supply filter caps.  The AK does not seem to
use electrolytic caps, at least there is nothing to indicate
that it does in the Ryder sheets.  I've seen references on
the list about ratings for AC.  Do the power supply caps
(2.0, 2.3, and 2.3 mfd) need to be selected for AC handling?
I had picked out some Panasonic E series metalized polyester
caps at 2.2 mfd and 400v for all three.  I didn't see any
orange drops in the catalog.  Should I use something else?
I had bought a spare AK chassis for parts and it had the
main power transformer melted down (tar all under the chassis)
but the filter capacitor can's wiring did not seem to have
overheated while the filter choke can's wiring had.  I never heard
of a shorted choke doing this sort of thing.
I am going to add a fuse near the power switch, should I try to
fuse anything else?  Enlighten me please, it's been a -long-
time since tech school at Keesler.
Thanks  and 73  Gary   gpewitt at execpc.com

-------------------------------------
Name: Gary Pewitt N9ZSV/KT
      6120 W. Calumet Rd. Apt 204
      Milwaukee, WI  53223
      414 355 8147 Home 414 297 4307 Work
E-mail: gpewitt at execpc.com
Date: 01/01/99
Time: 12:35:54


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