Author Topic: Converting a Kellogg Subset to a WE 634A Equivalent  (Read 5297 times)

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #15 on: November 13, 2015, 01:34:50 PM »
Interesting.... so is the 2F capacitor/condenser I added actually doing anything? Or is it just a nice decoration?

It is blocking direct current from reaching the receiver.

Without a capacitor, DC would flow from the line L2 through the secondary winding (S) via contact GN, the green lead into the receiver (RX), then the red lead via R and the primary winding (P) back to the exchange battery via L1 to complete the circuit.

Most receivers after a certain time were designed so that DC flowing through them had to be eliminated.

For this purpose the electrically ideal capacitor would be of infinite size, so that it does not affect the audio flowing through it. The value 2 F is an acceptable compromise to keep it reasonably small in the late 1930s.  Previous to that time, even a 2 F capacitor was rather large, but was in fact used just before WW-I.  Due to the war, materials were scarce and they decided to only use 1 F capacitors to save material. After the war stuffage, they just kept it that way, because it worked reasonably well and was cheaper.
In the case of the 534A subscriber set, as well as your Kellogg set, the capacitor can be shared between the ringer and the audio circuit.  Looking at my diagram, the ringer and the induction coil (S) are connected at the point C, therefore C carries no direct current, because the capacitor (C1) is located between L2 and C.

Using a separate capacitor for audio, one would disconnect the induction coil from point C and use the second capacitor to make the connection to L2 from the induction coil.  This leaves the existing capacitor working only for the ringer.

The benefit of the second capacitor is that it is a better size for the application, i.e. it has a lower impedance for audio. Also, since you are using a new capacitor, not a hundred year-old part, that it has no DC leakage, further improving results.

You can experiment and connect both the ringer and the induction coil to the existing capacitor, and if you rather have the original visual esthetics, you can remove the new one.

For an anti-sidetone subset, the second capacitor is a must, a single one cannot be shared with the ringer.  That was the original premise of your addition of it.



Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #16 on: November 13, 2015, 09:15:01 PM »
As I mentioned before, I hit a bonanza of Kellogg subsets recently (4). Three came from a seller who knows nothing about phones and looked like they had not been used for many decades.  A fourth came attached to a WE 202 phone, which appears to have been modified at some point.  Just for your interest, I am attaching pics of all 4.  The wiring diagrams posted earlier come from #2 and #1 respectively, which seem to be equivalents to WE 534 subsets, as pointed out.  As far as I can tell, these two differ only in the ringer design.  #1 had bad surface rust, so it is currently disassembled for painting. #2 is the one I modified.

All 4 are about the same size as the 534/634, in vented metal boxes that are held stuff by a single screw.
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #17 on: November 14, 2015, 09:21:43 AM »
Having some spare desk set boxes around is usually nice as you expand your collection.

I spent some time with the catalogs and it seems to me that these are F602 type subsets, as documented in Kellogg catalog No. 9, ca. 1928, on page 37 (attached). They are shown in the lower right corner.

F602-SA:1000 Ω, straight-line ringer
F602-BA:1000 Ω, biased ringer
F602-HA:harmonic ringer (16 2/3, 33 1/3, 50, and 66 2/3 Hz)
F602-HB:synchromonic ringer (30, 42, 54, and 66 Hz)

These are booster circuit (sidetone) subsets for three-conductor common-battery instruments.
The construction of these is indeed very similar to the construction of the WECo 534A, the only obvious mechanical difference being the attachment of the cover.

You have two types of induction coils, a No. 79A (visible) and the No. 99A (per your report).  The mechanical difference is that the 79A does not have the connection plate integral with the unit, whereas the 99A is a combined unit.

79A:  Primary 33 Ω, Secondary 17.5 Ω; 6 ounces, 4 5/8"  by 1" square spool heads
99A:  Primary 25.4 Ω, Secondary 7.8 Ω; 7 ounces, 4 1/4" by 1 1/8" and 1 3/8" deep.

It seems, these were intended to be used with the F118 manual desk stand and the F301 dial desk stands.

This type of subset was also made in an anti-sidetone variety with the model number 610.

Subset 1: F602-BA
Subset 2: F602-HA or HB
Subset 3: F602-SA
The subset (4) in your last picture has the guts, i.e. the induction coil and the ringer of a Western electric 634 set. It's hard to see, but I think the (wrapped) condenser is WECo-made also.
« Last Edit: September 04, 2017, 11:30:14 AM by unbeldi »

Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #18 on: November 24, 2015, 05:20:42 PM »
Picture "Slide2.jpg" shows a "normal" straight-line ringer, while the ringer in "Slide3.jpg" is the type of frequency ringer that I described earlier. This one must be the one that you described as vibrating only without striking the gongs. As can be seen, the clapper sits right in the middle between the gongs. In the other type, the clapper is pulled to one side by the bias spring.

Is there a way to make the frequency-selective ringer work, some type of adapter device to generate the right signal? The posts I've seen on this subject have suggested simply replacing them, but of course I don't seem to like being practical or doing this the simplest way....
« Last Edit: November 24, 2015, 05:24:02 PM by oyang »
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #19 on: November 24, 2015, 07:04:58 PM »
Picture "Slide2.jpg" shows a "normal" straight-line ringer, while the ringer in "Slide3.jpg" is the type of frequency ringer that I described earlier. This one must be the one that you described as vibrating only without striking the gongs. As can be seen, the clapper sits right in the middle between the gongs. In the other type, the clapper is pulled to one side by the bias spring.

Is there a way to make the frequency-selective ringer work, some type of adapter device to generate the right signal? The posts I've seen on this subject have suggested simply replacing them, but of course I don't seem to like being practical or doing this the simplest way....

I don't blame you!  I don't like doing that either.
In fact, it should be a crime.   :o

Building a frequency specific ringing supply is actually not that hard.  But easy is to use one of the few VoIP ATA's that can actually be set to those frequencies.  Asterisk can also be hacked to produce them on the TDM400 cards.

Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #20 on: November 24, 2015, 07:37:26 PM »
Building a frequency specific ringing supply is actually not that hard.  But easy is to use one of the few VoIP ATA's that can actually be set to those frequencies.  Asterisk can also be hacked to produce them on the TDM400 cards.

Do you have a source of information on how to build one?  Parts from RadioShack? I tend to like leaving things as original as possible, which is why I started this thread in the first place: I don't like the idea of tearing down a complete phone just to have a subset, even a common one. 

A second question: is there a list somewhere of induction coils describing which are sidetone versus antisidetone?  I was thinking of updating some old ringer boxes to be complete subsets by adding induction coils and capacitors.  The capacitors are easy to get, induction coils seem to turn up frequently. It seems like adding these to ringer boxes in the circuit configuration of 634A subsets would be straightforward. Some of those small ringer boxes are really attractive quartersawn oak and would be nice sitting next to a candlestick.
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #21 on: November 24, 2015, 09:29:00 PM »
Building a frequency specific ringing supply is actually not that hard.  But easy is to use one of the few VoIP ATA's that can actually be set to those frequencies.  Asterisk can also be hacked to produce them on the TDM400 cards.

Do you have a source of information on how to build one?  Parts from RadioShack? I tend to like leaving things as original as possible, which is why I started this thread in the first place: I don't like the idea of tearing down a complete phone just to have a subset, even a common one. 

A second question: is there a list somewhere of induction coils describing which are sidetone versus antisidetone?  I was thinking of updating some old ringer boxes to be complete subsets by adding induction coils and capacitors.  The capacitors are easy to get, induction coils seem to turn up frequently. It seems like adding these to ringer boxes in the circuit configuration of 634A subsets would be straightforward. Some of those small ringer boxes are really attractive quartersawn oak and would be nice sitting next to a candlestick.

Well, Radio Shack probably has some useful parts, but you have to look elsewhere.
I have a Panasonic PBX that I have adapted to ring frequency ringers. It only involved feeding the frequency signal from a signal generator into the right spot, and using the ready made mechanism in the PBX to do the rest.  A signal generator can be bought for a few dollars.
I also have built some standalone ringing generators with PAM8403 class D digital audio power amplifiers, available for pennies almost from China, driving a low-voltage transformer in reverse.

Western Electric induction coils are documented in Bell System Practices.  Search for Section C31.401 Issue 1 1933-11-22, for the early induction coils up to that time.
Here is an excerpt I use in my documentation.  I have also more extensive tables for my use.  There is also another BSP from the 1950 or 60s for induction coils.

I don't know of any charts for other manufacturers.  Usually it is necessary to sift through the catalogs.
« Last Edit: September 04, 2017, 11:32:03 AM by unbeldi »

Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #22 on: November 25, 2015, 01:27:08 AM »
I also have built some standalone ringing generators with PAM8403 class D digital audio power amplifiers, available for pennies almost from China, driving a low-voltage transformer in reverse.

Thanks for the info.  Would you be willing to share specifics on how to build the PAM8403 ringing generators and calibrate to the ringer?

Otto
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #23 on: November 25, 2015, 10:26:03 AM »
I also have built some standalone ringing generators with PAM8403 class D digital audio power amplifiers, available for pennies almost from China, driving a low-voltage transformer in reverse.

Thanks for the info.  Would you be willing to share specifics on how to build the PAM8403 ringing generators and calibrate to the ringer?

Otto

This is my basic design and the only formal diagram right now. It's really just three components, generator, amplifier, and transformer. The added resistor just functions as stuff circuit protection to limit current draw.
The frequency generator can be implemented in many ways. A ready made function generator is the easiest, but I also have used a little Arduino board supplying a waveform using pulse width modulation.
These Class D amplifiers are widely used to drive low-impedance speakers (<10 ohms) directly, in lap-tops and all kinds of small portable music/audio players.  Cost ~ $1.  The transformer is used in reverse, to transform a 5V AC signal to ca. 100V.

Don't take the circuit inside the box too literally, it's just to indicate an amplifier is involved, the actual implementation is rather different on the board from an op-amp. The board is only about a half inch on each side. Not shown in the diagram is its 5V power supply.

PS: Here is a brief introduction and view of a modified Panasonic PBX for frequency ringing:
http://www.classicrotaryphones.com/forum/index.php?topic=11948.msg127016#msg127016
« Last Edit: September 04, 2017, 11:30:24 AM by unbeldi »

Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #24 on: November 25, 2015, 05:01:00 PM »
I think you markedly overestimate my skills! My ability to implement will need more concrete instructions like x is connected to y on your Kellogg subset ringer...... Hopefully it's not too much trouble to ask for that guidance.  I'm going to track down the PM8403 class D part, and beg you for help from there....

Embarrassedly,

Otto
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #25 on: November 25, 2015, 05:35:53 PM »
I think you markedly overestimate my skills! My ability to implement will need more concrete instructions like x is connected to y on your Kellogg subset ringer...... Hopefully it's not too much trouble to ask for that guidance.  I'm going to track down the PM8403 class D part, and beg you for help from there....

Embarrassedly,

Otto

I didn't want to be the one spreading discouragement, lol.
You asked for the principle, and I shared it.  I think that's about as far as I can be of help.  And as shown, it is only for ringing a telephone otherwise not connected to the telephone network.
That's where the PBX solution is much easier to work with.



Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #26 on: November 25, 2015, 07:24:23 PM »
Ha, thanks!  So excuse my ignorance, but the signal going to the ringer from the circuit in the subset should be known, and what the ringer needs is known.... there is no simple electronic way to make the conversion with one transformer that you simply insert in series between the two?
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #27 on: November 25, 2015, 08:24:56 PM »
Not sure what you're suggesting.
You can certainly plug in the subset (or any phone) into the output of my transformer,  but that doesn't make the telephone useful for talking.

For a complete configuration, to use this in a normal telephone hookup, one has to detect ringing from the telephone company, or from some other source such as an ATA, and replace this ringing signal with the output of my generator, typically with a relay or electronic switch to prevent ringing current to be sent back to the line.   This is exactly how electronic key systems work, such as the Panasonic type I referred to.
So, it is easy to build a ringing generator to demonstrate the sound of a frequency ringer.  But from there on it gets more complex.

Offline oyang

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #28 on: November 25, 2015, 08:37:21 PM »
Oops; guess I wasn't clear!  I was asking whether the frequency-specific ringer could be made to ring.  Right now the clapper in the ringer in the Kellogg subset vibrates weakly because it's not getting the right type of current.  My question was whether somehow I could add an electronic element to the subset to make it ring, some type of adapter.
"In theory, theory and practice are the same. In practice, they aren't."

unbeldi

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Re: Converting a Kellogg Subset to a WE 634A Equivalent
« Reply #29 on: November 25, 2015, 09:41:38 PM »
It depends how far the frequency is off from 20 Hz.   I am not sure we established the frequency of your ringer.  Are there any markings on the ringer anywhere?  I got a box full of Kellogg ringers, and IIRC most or all have markings on the armature that pivots during ringing.

If it is not too far off 20 Hz, say 30 or 33 Hz, it may be possible to raise the value of the ringing capacitor which would lower the electrical resonance a little.  I haven't tried it with Kellogg ringers.