12/23/2022
Is there a preferred type of capacitor that is best suited for these antique radios? i.e. - Mica, polymer, ceramic, niobiom oxide, film, aluminum polymer, tantalum, etc. Will a cheap Orange Drop cap work just as well as a more expensive type?
PS - restoring a 53-1750
Thanks
Mica typicaly is for low capacitance/hi stability.
For anything else, other than electrolytics, there is the film type.
for me it depends a bit electrolytics GENERALLY get replaced with like items UNLESS i can find a film cap that will fit of the correct voltage and value. this was the case in two hallicrafters radios. and my philco 84 has no e caps in it the can has two films in it this doesnt happen very often. micas fail too especially when they have high dc on them if that happens then its a modern c-d silver mica BUT sometimes a cog/npo mlcc can be used in their place, available lead length depending and i like muratas. for the most part people talk about the notorious bumble bees or wax/paper/foil types. its film caps for this either radial or axial . its important to try and install the replacement in the same location to avoid lead dress issues if in doubt make sure its where the old one was but its going to be smaller with any modern part you use and so lead length becomes an issue. axials while having an inductive component are by their nature longer BUT radial orange drops are a better choice sometimes as they fit better sometimes like around tube sockets and terminal strips. its difficult to put into words but like the man said about the value of real estate, location,location,location. my hallicrafters sx62 has nothing but orange drops that are stacked film and i listen to it every day.
Yes I also use film caps to stuff the electrolytics if one with the proper capacitance can be found. I use Solens, or whatever sold in AES or Mouser.
This said, good quality (Panasonic or Rubycon, or Chemicon low ESR / High Ripple current) electrolytic caps are just fine to be used. They are smaller size, and if one worries about 450V net being enough (though this is what was used in the original factory chassis'), two of them of twice the capacitance could be serialized to achieve the required capacitance and double the voltage, with the ripple current specs still kept. Those I use are 22uF/450V Panasonic ones, and their ripple is on the order of 670mA which is many times that needed. Considering the service hours formula contains voltage, current and the ambient temp, 105 degrees ones with double the voltage will serve forever and will certainly outlive any of us here, and maybe even the next generation.
PS. I do not use the leakage equalising resistors across the serialized caps as any single cap is still capable of withstanding the full voltage.