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Replacing circular ceramic capacitors with???
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krho:
I'd say that the capacitance is .022uF=>22nF
Richard Crowley:

* It is unlikely that the value of the capacitor changed as a result of the slight chip.  It is probably within the original tolerance of the nominal value.
* It is unlikely that the exact value of the capacitor is critical in that particular part of the circuit.
* It is unlikely that the voltage rating is critical in that particular part of the circuit. If the voltage gets anywhere near even 50V you will have much bigger things to worry about than that capacitor.
Unless you intend to use this in a high humidity environment (like on a ship or submarine?) it may be better just left alone.  If you are that worried about, seal up the chip with a dab of epoxy, etc.


SeanB:
As those are wax dipped, the simplest fix for them is a drop of candle wax on the capacitor, and a quick blast of hot air to melt it into the capacitor body again. Will reset the aging of the capacitor, but as it is a disc ceramic and will drift anyway, and as it has a -20% +80% tolerance, and will drift in this range anyway, resetting the aging with heat will not have any real consequence on use.

You might want to resolder the diode though, as it is going to cause problems with offset voltages, as the diodes are there to decouple hum, and the capacitor is there to reduce high frequency noise, so in use anyway will only have 0.6V across it maximum.
KD4CCF:
Is it intended that back-to-back diodes would go on each BNC? At most you'd see 1.2V across the capacitor(s). Just about anything would work.
David Hess:
Practically any ceramic or film capacitor will work in this application and the value does not need to be exact; a 0.015uF or 0.027uF would work just as well.  As KD4CCF pointed out, a lower voltage part is acceptable because the diodes limit the voltage.

A 0.022uF 50V 10% X7R multilayer ceramic capacitor is probably about the least expensive option and better than the original dielectric.
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