293A sub set causes busy signal

[Sargeguy]

I have a 293A subset which for some reason uses a No. 46 induction coil along with the 21-D condenser.  It is wired as a normal 293A but generates a busy signal when plugged in.  I remember that the No. 46 was used on a "booster" circuit, but do not know what that means.  

Here is how it is wired:

L1:  #1 & Black ringer wire
G: Not connected
L2: Condenser (upper)
C:  Condenser (lower) #4 & Grungy white (Red) ringer wire

The coil shows 14 ohms between 1 and 2 and 9 between 3 and 4

The ringer checks out when tested seperately.  

Any suggestions?  How do you test if the condenser is good?

[Phonesrfun]

Use an analog ohm meter.  One with a needle meter.  Connecting it across the capacitor should make the meter jump slightly and then go back to showing an open circuit with infinite resistance.  Reversing the leads on the cap will once again cause the meter to momentarily jump, and then once again settle back to reading open.

If you get low resistance, the capacitor has a leak, which could cause a busy signal.  By the way, those old capacitors were notorious for getting leaky (current wise.  I don't mean a physical loss of liquid although that sometimes happens too).

I have some modern 2mF caps @ 250 V if you need a replacement.

[Sargeguy]

I found some modern capacitors the other day when I was digging around, labelled 1MFD 100VDC and 2MFD 100VDC, would the 2MFD be suitable even though it's only 100 volts?  Do I need to disconnect the 21-D to test?

[Phonesrfun]

Yes, test the cap all by itself.  Connection with other components can mess with the results.  Ringing current is 75-80 volts.  Normally a cap should be rated at twice the voltage as a margin.  Normally 100V would be too "tight" in its rating, and risk the cap breaking down, which would get you right back where you are with the old one (if that's what is the problem).

That being said, I would not have any problem substituting the 100 V one just to see if it would work properly with the newer cap.  It is not likely to break down with just a few rings.  Try it out.  You can't hurt anything but the 100V cap.

If it works with the newer cap, I can send you a 250 volt version.

[Sargeguy]

I hooked one end to L2 and another to C and I got tone instead of the busy signal so it appears to be working.  I did not disconnect the 21-D since it was soldered and   I am too tired to bypass it.  It took all my brain capacity to get this far!

[Phonesrfun]

Sounds good. See PM