meissner: Keep Caps in Kit

Fellow Radiophiles:

When I repair/restore a radio, I like to keep as many of the original components as possible in the radio. Recently, I started to replace bad or leaky paper capacitors in place.

The method is to cut one of the bad capacitor wires, and insert a small ceramic capacitor of the same value, and then short out the bad cap with a wire. This tends to preserve the apperance of the chassis and retains historical integrity in the set better than with hollowed out bad caps with new caps inside. These repairs can also be easily reversed.

 

Another type of capacitor to consider as very small substitutes, are the modern multilayer chip capacitors. Yesterday I tested several values of COG capacitors between 0.1uF and 100pF that were rated for 50V operation, and I found much less than 1uA leakage at 400V. These caps were about 0.1" long, which is still easy to handle with tweazers. Leaded caps in this size range can also be used.

I plan to continue exploring the suitability of these capacitors for nearly invisible leaky paper cap repairs. I will apply higher voltage to find their breakdown voltage and leave the chip caps powered up over a long time at high voltages to identify any voltage stress effects. If I can manage elevated temperature for the long term cap test, I will do that too.

Regards,

-Joe

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