What does everybody use for molded capacitor replacement?

[CJVx]

I’m talking about rectangular caps that are often similar looking to mica caps, domino etc. apparently they are molded paper capacitors, mostly in picofarad values and are often times in a mode of failure just like standard looking paper capacitors. I’m reluctant to use ceramic disc capacitors in place of these since most sets have plenty of ceramic disc capacitors in them already, so why wouldn’t the manufacturer just use them for these applications. Thanks.

[ChrisW6ATV]

My thoughts are: First, verify on the schematic diagram and parts list the exact value of the parts. There were some wax/paper capacitors smaller than .001uF in old equipment, which translates to less than 1000pF of course. If yours are, say 470pF that is the same as .00047, probably rare in wax/paper but possible, and any modern "film" capacitor may work fine.

It will likely not hurt to use modern mica or silver mica capacitors in those locations (or anything under .001uF), if you can get them with the proper voltage rating.

[Electronic M]

Any cap of that type 1000pF or higher I just use film caps (same ones I replace papers with) and it's never been a problem.

[bandersen]

Yes, polyester or polypropylene film caps. Don't use ceramic as they drift in value with temp and applied voltage.

[Tim Tress]

If you're thinking about the big Micamold molded capacitors used in the 1940s and early 1950s sets, they are paper inside, and are always leaky now. Philco also used some square molded 0.01 mfd caps, and they are just as bad. Standard film capacitors will replace them.

[Tube TV]

I've been replacing them with film caps. The last while I have got in the habit of testing the mica caps when working on a set. I've ran into a few that have been leaky and caused intermittent troubles.

[CJVx]

As of late, I’ve been using high voltage SMT NP0 ceramic capacitors that I install on adapter boards I’ve designed to occupy the space of a mica or molded capacitor. NP0 caps have practically no drift over temperature range and are extremely inexpensive, although it’s going to take a while to absorb the cost of getting my adapter boards produced.