I have an old radio that has a "domino cap" between the plate and cathode of a 50B5 audio output tube. The dots were never colored on it. It appears to be a Micamold brand (hard to read). It has 3 uncolored dots between arrows, and one more dot above them.
Instead of coloring the dots, there is this [ CA-281 ] stamped on it. Does that mean anything? Or is that a manufacturer part #?
The schematic says it's supposed to be a .01uf @ 600v. This is a Abbotwares Z477 radio from 1947.
Normally I dont even bother with those mica caps, since they do not normally go bad. However, this radio had one lead to that cap cut, so there is likely a problem with it. (Maybe)??? (or it was worked on by someone who dont know much)...
After I replace the nasty looking filter cap and a few other caps that look very bad, I will plug it in. Then I will clip this cap back into the circuit and see if it really is bad or not....
Anyhow, if I want to replace it, what is the best replacement. Can I use a ceramic disk, or should I try to locate a mica (probably wont be easy to find), or just use a modern tubular cap rated at 600v?
The old one is reading 9.73 NF with my meter, so that is close to the correct amount. (Of course there is no voltage on it, so it make breakdown when voltage is applied).