Author Topic: Western Electric 634BA - Ringer Capacitor question  (Read 561 times)

Offline Fennec

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Western Electric 634BA - Ringer Capacitor question
« on: June 10, 2017, 08:40:10 PM »
I am working on a 634BA subset to pair up with a 202, and came across an interesting anomaly - the ringer capacitor is actually 0.5 uF vs. 1.0 uF that schematic shows...
Furthermore, it looks like a previous owner has attempted to install another 0.5 uF in series with the original...

Question - was this done in an attempt to lower the REN of the ringer?

For reference, the induction coil in this one is identical to the 302 I almost finished, i.e. 101A.
Ringer coils are 4,600 Ohm total resistance, and also look like a 302 with smaller brass bells.

I have to add that both the capacitor and the ringer seem to have been fitted at the factory - bolts are the right length, bracket for the ringer is correct and holes line up properly with the base.

« Last Edit: June 10, 2017, 08:59:00 PM by Fennec »

Offline poplar1

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Re: Western Electric 634BA - Ringer Capacitor question
« Reply #1 on: June 10, 2017, 08:48:49 PM »
Since you have the same B1A ringer found in 302s, then it should also have the same value for the ringing capacitor -- 0.5 uF.

For 634BA subsets, this B-type ringer is found much more often than the older numbered type ringers with two 2150 ohm coils.
"C'est pas une restauration, c'est une rénovation."--François Martin.

Offline Fennec

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Re: Western Electric 634BA - Ringer Capacitor question
« Reply #2 on: June 10, 2017, 09:01:11 PM »
OK, thank you - this explains the 0.5 uF cap. The one added by someone in series though - would this be an attempt to lower the ringer REN?

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Re: Western Electric 634BA - Ringer Capacitor question
« Reply #3 on: June 10, 2017, 10:54:29 PM »
I am working on a 634BA subset to pair up with a 202, and came across an interesting anomaly - the ringer capacitor is actually 0.5 uF vs. 1.0 uF that schematic shows...
Furthermore, it looks like a previous owner has attempted to install another 0.5 uF in series with the original...

Question - was this done in an attempt to lower the REN of the ringer?

Two 0.5uF caps in series would result in a capacitance of 0.25uF

Two 0.5uf caps in parallel would result in a capacitance of 1.0uF


0.25uF is quite low for a ringer capacitor so am also wondering why they did that and what effect if would have on the REN.

Alex G. Bell

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Re: Western Electric 634BA - Ringer Capacitor question
« Reply #4 on: June 10, 2017, 11:01:39 PM »
Two 0.5uF caps in series would result in a capacitance of 0.25uF

Two 0.5uf caps in parallel would result in a capacitance of 1.0uF


0.25uF is quite low for a ringer capacitor so am also wondering why they did that and what effect if would have on the REN.
I'm not sure what effect it would have on the REN either.  But ringer circuits are generally electrically resonant at 16-2/3 to 20 Hz and this would double the resonant frequency, whatever that is, so it probably would reduce the sensitivity and make it prone to not ringing when ringing voltage is low due to other ringers loading the line and other causes (VOIP ATAs which don't put out much in the first place for example).