[Milsurplus] BC-348-R Paper Capacitors

[k2cby]

The BC-348-R uses two varieties of .01 uF postage stamp capacitors. 

Part numbers beginning 12- are micas and seem to be in good shape.

Part numbers beginning 11- are rectangular black paper capacitors are .01 uF
10% capacitors rated at 500 volts and used in non-critical plate and bypass
applications. I discovered that one of these had shorted and taken out the
dropping resistor associated with it. This prompted me to pull out one of
the other paper caps.

My Heathkit capacitor checker showed "bad" with any voltage above 50 or so
applied. In the bridge mode I could not get a null, but my digital capacitor
meter showed .01 uF - right on the money.

I then decided to see "just how bad" and connected the cap to a variable dc
supply. With 250 volts applied (the BC-348 uses just a bit over 220 volts
B+) the cap drew 220 uA, corresponding to a resistance of about 1.16 Meg.

I checked a couple of other "11-series" capacitors with the same result.

In today's world a capacitor with these specs wouldn't pass muster. Before I
yank out and replace all of them, I wonder whether these were passable
values for a bypass capacitor in the 1940s with "a war on." 

Any thoughts?

 

Miles B. Anderson, K2CBY
16 Round Pond Ln.
Sag Harbor, NY 11963

k2cby at optonline.net

 

 

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