Dumb Capacitor Question

[Charlie]

This was briefly mentioned in Mike's thread, and I've heard it mentioned before by some... so could someone explain?

It's been said that with some circuits, it's best NOT to use ceramic disc capacitors in places where orange drops would be normally be used. For instance, .01's, .001's, .047's. I have, on occassion, replaced old paper/wax .01's with a ceramic disc. Usually, I use ceramics with voltage ratings much higher than the set needs. For intance, if I need a .01/400v cap, i'll use a 1kv ceramic just for added peace of mind, and because I have a shit load of them at times. I would think that today's ceramic discs would be far superior than the paper/wax caps from years ago. But, many say that using orange drops or mylars are better.

Is there a specific reason to steer clear of ceramic discs in some applications? Are they too unreliable?

[Bob]

Some folks feel that ceramics mess with the sound if they're in
the sound path. The order, in general, is film types first, then electrolytics (probably non-polarized), then ceramics.

The general feeling is that if you're going to spend time doing this once, then use the better/best ones you can find.

[peverett]

All capacitors, due to how they are manufactured have parasitic resistance and inductance. This is different for the orange drop vs ceramic. I would guess that this might affect the video, IF, and sound IF/dectector circuits, but do not see how the audio would be affected as the frequencies dealt there with are very low-15khz or lower.

I do not believe that reliabilty is the issue almost all capacitors made today are hundreds of times more reliable than the ones made in the 1950s.

The area to stay clear of is using ceramic caps to replace the coupling caps used at the CRT deflection plates of electostatically-deflected sets (7JP4 types). There are documented cases of scanning nonlinearities that occurred when ceramic caps were used as replacements. This would indicate not using them as audio coupling caps as well.

In RF coupling and bypass applications they are fine, in fact very reliable.