Adding or Repairing a Ringer Set - do I use a .47uf or 1uf capacitor?

[wds]

I've been working for a while on a few ringer boxes, and have had a certain amount of trouble figuring out how to properly wire a ringer.  Whether it's repairing a broken ringer box, or building one from scratch, it seemed there were several schools of thought about which size capacitor to use.  There are many posts in this forum that help with this dilemma, but as with all posts, after a period of time they become almost impossible to find again, even using the search method.  I thought I would create a new thread strictly for this topic that would be easy to find a year from now.  I tried to use all the right buzz words in the subject line, but if anyone thinks a different word might be more appropriate, I would be happy to change it a little.  If you have any information that would benefit laymen like myself, please post!

[wds]

I located a 1.0uf cap from Radio Shack, and some .47 uf caps from another source.  I noticed right away that the 1.0 uf allowed the bell to ring much louder than the .47 uf.  Can someone explain why?  Is .47 the wrong size to use for ringesr?

[wds]

After reading some in the Old Time Telephone book by Ralph Meyer, (table 6-1) it seems that the correct cap for an older ringer is a 1 uf, as it gives better matching of resistance to the ringer, especially anything older than the 302 ringer.  The 302 ringer (and newer) has a much higher resistance, and was designed to use a smaller cap, ie, .47uf, to help reduce the size of the cap.  The older 1uf caps were quite large, and by changing the impedance on the ringer,, they could use a much smaller cap.  But even testing the 302 ringer I still noticed that the ringer was louder using a 1 uf cap as compared to the .47 cap.  As the size of the modern caps are so small, it seems that the correct cap to use in almost all cases is the 1 uf, and not the .47 uf.   Radio shack part # 272-1055 seems to be the best cap to use with these older ringers.  Does anyone else have any comments about their use of different size caps?

I have a bag of .47 uf caps that I'll make someone a good deal on............

[wds]

One more link to a post that also has some info. about the ringer resistance and the correct cap. to use.

http://www.classicrotaryphones.com/forum/index.php?topic=6244.msg74391#msg74391

[LarryInMichigan]

The impedance (AC resistance) of a capacitor is inversely related to the capacitance value and directly related to the frequency of the current.  A 1 μF capacitor will therefore pass more current than a .47 μF at the same frequency.  You can always reduce the amount of current flowing through a ringer by adding resistors in series with the ringer.  Also, you can increase the capacitance and therefore the amount of current flowing through the ringer by connecting capacitors in parallel.  You can easily create a 1 μF capacitor by simply connecting two .47 μF capacitors in parallel (just twist each lead of one with a lead of the other) , so don't discard your stock of .47 μF capacitors.

The physical dimensions of the capacitors are irrelevant, as long as the voltage rating is sufficient.

Larry