Older Rotary Phone, Help Identifying?

[Matilo Telephones]

These old capacitors were sealed with some sort of bitumous substance. It sometimes turned gooey, but hardened with time.

The insides of the capacitor sometimes expand over time. It even can burst the casing open.

These two effects combined may explain what you see here.

[lmd]

Reviving this post from a long, long time ago.  I cannot believe that over 18 months have passed since I last had a chance to look at this old phone!  Time flies with life, work, and family.

I spent some time on Sunday working on the phone mentioned in this thread.. and happily I made some progress!

The capacitor leakage seemed to be paraffin wax mixed the the crunchy bituminous substance that Arwin mentioned.  I carefully pulled the terminal plate away to reveal another phenolic (?) plate that secured the terminals to leads into the capacitor itself underneath.  I carefully scraped away a little bit of wax to flatten the surface and cleaned out the leakage before putting back the terminals and plates - it seemed that the capacitor itself was fine.  The capacitance meter on my DMM indicates 2.7uF and I couldn't detect leakage across the cap.

The receiver element in the mouthpiece seems to be functional too - bonus!

The dial wiring did not seem right so I made notes and removed it.  I connected it to my VOIP ATA and confirmed that I could hear a dialtone and hear myself in the earpiece.  The ringer was working but needed some adjustment.  It seems to be a bit of a different design from some of the ones described here.  I attached a close up photo after removing the hook switch plate.

There are a few quirks that I am hoping forum members may be able to help me figure out:

1.  Bell Tap on Hook Switch action
When the hook switch is depressed, there is a 'bell tap'.  I connected "Ek" to "La" and then used "La"=ring/red and "Lb"=tip/green.  If I reverse the tip/ring the bell tap occurs when I release the hook switch.  Is this normal?  I haven't been able to find a bias spring or see anything in the mechanism that would correct for this.

2.  Dial Wiring
I was comparing the wiring diagram inside the telephone to the basic sidetone circuit.  The induction coil has two windings so I think this is correct.
The dial wiring is confusing me.  Referring to "Old Telephones" by Jeffrey Race (PDF I found), it seems like the pulse switch in the dial should break/make the connection between L2 and transmitter.  The diagram in the phone appears to short out the "T" terminals (receiver/earpiece element).  I attached a comparison to help show what I am thinking.
The dial I have (labeled "M-2" on the body and "5751A" on the terminal block mount) appears to match the attached "Figure 11" wherein the shunt spring shorts BK, BB, and W together when the dial is turned.
Is there a diagram I could use as a reference to try rewiring the dial properly?  I searched and couldn't find a post that helped explain things to me.

3.  Feedback
On occasion I hear howling/feedback on the handset when it is picked up.  Is this normal with a sidetone circuit?


Thank you again for support and suggestions.  I feel badly for not getting back to this sooner.

Dan

[dsk]

You are both right.
This telephone are more or less a copy of an instrument made in Antwerp in the early 1920ies. The diagram drawn with in the post over are right.
In Norway the terminals for the Transmitter=Microphone (Norwegian: Mikrofon) are marked M and the receiver here named with the Norwegian name: Telefon (English: Telephone) probably under influence of e.g. the German term Fernsprecher where the receiver terminals are F.

Looking at the original drawing of the dial, the left set of contacts are the pulse springs, with a symbol inspired of two contacts normally closed where a flying cam will pass in the middle and open the contacts for each break, (Matilos page) 

When it comes to making of Dials, the Norwegian made dials did not become reliable before they actually started with the design of your dial, so finding a Norwegian made dial from before WWII is not easy.

dsk

[Matilo Telephones]

Dan, I have at least 2 projects on my bench that are over 2 years old. :-)

Anyway, no 1 about the ting: that is normal for these early models. You can perhaps prevent them by adding a bias spring. Personally I like to leave it, because it is Original.

2 perhaps I have missed something and I do not quite follow. Why do you want to rewire it? Does it not work properly?

3 The howling: is it reminiscent of an old valve radio? It may be that the coil is faulty.

[lmd]

Looking at the original drawing of the dial, the left set of contacts are the pulse springs, with a symbol inspired of two contacts normally closed where a flying cam will pass in the middle and open the contacts for each break.

dsk, you are absolutely right about the contacts - the photo and your description helped me understand that the pulse contacts are between "Lb" and "M" and not between "T" terminals.
I was wondering why the connection named "S" (between "Lb" and "M") was missing on the terminal block but shown in the diagram.  The reason is obvious to me now - the pulse switch in the dial is making and breaking that circuit.

Here is a corrected diagram.

Anyway, no 1 about the ting: that is normal for these early models. You can perhaps prevent them by adding a bias spring. Personally I like to leave it, because it is Original.

I agree - I like the ting sound and it isn't worth trying to work a bias spring into the mechanism.

3 The howling: is it reminiscent of an old valve radio? It may be that the coil is faulty.

I think the induction coil is okay - I check the resistance and found 45.6 ohms across 1-2 and 21.8 ohm across 3-4.  The coil itself seems to be marked:
1-2: 1750W 0.22 44
3-4: 1250W 0.22 22
If the last digit is DC resistance then it is fairly close.


In terms of wiring...
I am still confused about wiring the dial that came with the phone.  It wasn't working so I removed it from the circuit to test the transmitter/receiver/ringer.  I will try to explain what is confusing me here.

Original dial:
The schematic diagram and photo of the original dial that dsk posted appears to have separate pulse and shunt switches. 
The pulse switch opens between "Lb" and "M".
The shunt switch bridges the earpiece at points "T".
The microphone/transmitter is not shunted.

Dial To Be Installed:
The (Spanish?) "M-2" dial that I received with the phone has a different switch configuration.
The pulse contacts share a connection with the shunt spring/switch.  I attached a diagram and photo.
I looked at some wiring examples (in "Old Telephones" PDF file) and the examples show the shunt switch will shunt both the receiver and transmitter elements to remove them from circuit.

Wiring Proposal:
I attached a diagram with proposed wiring connections but I am not certain that it is correct.
The pulse switch remains between "Lb" and "Mx" (dial pin "1" and "2") - should be similar to the original dial.
The shunt switch on pins "3" and "4" can cross between the "T" terminals - should also be similar to original dial.

The shunt switch connects pins 2-3-4 which deviates from the original dial.  Is it acceptable to have the shunt in the dial connect "Mx" to both "T" terminals?  In theory "Mx", "My", and the right-hand "T" terminal are connected together when the hookswitch is released (handset picked up).

I hope that might help explain what is confusing me... and I hope my explanation does not confuse you

Dan

[dsk]

Should be perfect.
Another telephone made at same time may be this one: http://tinyurl.com/j54qwq5
Your version has a use of the capacitor to boost the transmitter signal, this was modified away for  some phones. I do not know why, but the howling (acoustic feedback) cold be a reason.

If you are using a pulse to tone adapter on the line, e.g. dialgizmo it might be needed to move one of the shunting contacts (orange in your schematic's) from T to A.

The REN load of this telephone with huge capacitor is enormous.  If that causes problems, try to replace the strap between EK and A with a capacitor of e.g 1 microfarad. 

dsk

[lmd]

If you are using a pulse to tone adapter on the line, e.g. dialgizmo it might be needed to move one of the shunting contacts (orange in your schematic's) from T to A.

I am not sure that I follow the change that you described.. would this be moving one of the shunting contacts at "T" to the "La" line input terminal?  I am considering the use of a pulse-to-tone adapter, or finding a VOIP ATA that supports pulse dial.  I think there is a Grandstream model that does this.

The REN load of this telephone with huge capacitor is enormous.  If that causes problems, try to replace the strap between EK and A with a capacitor of e.g 1 microfarad. 

dsk

I think you mentioned that the ringer may draw a higher current.. would that be a noticeable issue and what would be observable if this was an issue?
Are there any other problems that a high REN might cause.. like affecting DSL internet service or causing some damage on the telephone line?  I have been testing with a Cisco SPA122 ATA because I didn't want to put this on my actual phone line until I know everything is working properly.

I partially took apart the dial (the back side) to lubricate the main shaft as well as the gear between the main gear and governor.  It is operating more smoothly now.
I did not take apart the front-side spring and dial wheel because I was not able to find any documentation/photos showing the internal parts of this dial.  Do you know who the manufacturer was?  I thought it might be an AE based on the topology of the switches but it does not look anything like the AE dials I was able to find on the forum.

I attached two photos here for reference..
  - one of the front side with the label/center cover removed
  - one of the back after I disassembled the mechanism
..maybe someone else will be looking for photos of this type of dial?

In terms of cleanup, I found that #0000 super-fine steel wool was very effective.  I was able to clean up the handset and rubber grip.  The rubber has an interesting coloured appearance.. I am not sure if it is staining or if the rubber looked like that when it was manufactured.  Either way, I like it

Is there a specific type of polish that could be used to buff the metal components of the handset?  I assume these are treated with some sort of (nickel?) plating.  I buffed them with a little bit of Turtle wax but there are some "cloudy" areas that don't seem to buff away.

When the weather gets warm enough to work outside I plan to paint the black case.  It is fairly badly chipped and some flaking of paint on the back.  Someone had brush-painted with black metal paint at some point in the telephone's lifetime and I think I could improve the coating.

I wanted to attach a photo of the ringer mechanism as well because it might be interesting to someone looking for photos of the mechanism.  I made adjustments so it is striking both bells.. before it was only striking one.  I had to loosen the hex sleeve with the red (center of photo) to increase the movement slightly. The loosening the tiny hex sleeve directly above allowed me to center the clapper.. and then tighten it after adjustment.

Thanks again for the help and advice   By the way, I think this thread has changed into the restoration of an old phone more than yard sale finds.. should I start a thread in another area for this discussion?

- Dan

[dsk]

The REN load of this telephone with huge capacitor is enormous.  If that causes problems, try to replace the strap between EK and A with a capacitor of e.g 1 microfarad. 


I think you mentioned that the ringer may draw a higher current.. would that be a noticeable issue and what would be observable if this was an issue?
Are there any other problems that a high REN might cause.. like affecting DSL internet service or causing some damage on the telephone line?  I have been testing with a Cisco SPA122 ATA because I didn't want to put this on my actual phone line until I know everything is working properly.

High REN load will usually not ruin the adapter, at least I have never heard abut that. The high load may give a false signal like lifting up the receiver and put it back at once when it rings. OR It may be to hard for the line to operate the ringer(s). You just have to test it out.  My old PAX from 1940-something does not like this phone, and did see it as lifting off and hanging up at first ring.

dsk

[dsk]

If you are using a pulse to tone adapter on the line, e.g. dialgizmo it might be needed to move one of the shunting contacts (orange in your schematic's) from T to A.

I am not sure that I follow the change that you described.. would this be moving one of the shunting contacts at "T" to the "La" line input terminal?  I am considering the use of a pulse-to-tone adapter, or finding a VOIP ATA that supports pulse dial.  I think there is a Grandstream model that does this.

For the first only do this if you experience problems when dialing.
The reason to do this is to indicate a difference between dial and hold, and just doing nothing. Only worth trying if you get problems with dialing. 

dsk

[unbeldi]

I partially took apart the dial (the back side) to lubricate the main shaft as well as the gear between the main gear and governor.  It is operating more smoothly now.
I did not take apart the front-side spring and dial wheel because I was not able to find any documentation/photos showing the internal parts of this dial.  Do you know who the manufacturer was?  I thought it might be an AE based on the topology of the switches but it does not look anything like the AE dials I was able to find on the forum.

I attached two photos here for reference..
  - one of the front side with the label/center cover removed
  - one of the back after I disassembled the mechanism
..maybe someone else will be looking for photos of this type of dial?

The dial looks to me like a BTMC 7000-series dial.

Is there a model number stamped on that little triangular plate that holds the gears in place?
It might be a 7019A or close.

I don't recall having seen one with a Lucite or otherwise transparent finger wheel. That must be from the 1950 or later?

[dsk]

If you are going to paint it, it may have signs after a decal like this:

or the coat of arms.

With one of these dial centers:



dsk