Author Topic: Tesla Phone  (Read 3740 times)

Offline LarryInMichigan

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Tesla Phone
« on: May 06, 2014, 11:54:21 PM »
I picked up this Tesla phone dated 1949 last week and am just starting now to try to restore it.  Can someone tell me what the model is and how it should be wired?  There are markings by some of the terminals, but some are illegible and others are missing.  Also, suggestions on where to obtain replacement rubber feet would be appreciated.

Thank You

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #1 on: May 07, 2014, 01:18:51 AM »
Hey Larry, that is a W28, licence built. Does not look too different from the other versions.

Nice and interesting find.

On German ebay there are plenty of parts.

The upper wiring seems to be ok. Is there something wrong with the inside wiring?
« Last Edit: May 07, 2014, 01:21:25 AM by Matilo Telephones »
Groeten,

Arwin

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Offline paul-f

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Re: Tesla Phone
« Reply #2 on: May 07, 2014, 01:20:38 AM »
Visit: paul-f.com         WE 500  Design_Line

.

Offline LarryInMichigan

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Re: Tesla Phone
« Reply #3 on: May 07, 2014, 09:33:21 AM »
I believe Tesla called it a model K.
 
This might help find more on European sites.
 
http://www.telephonecollectors.info/index.php/document-repository/doc_details/655-tesla-table-telephone-model-k-automatic-operation

Thank you for the link.  It is very interesting.  Apparently, Tesla was promoting this phone for export.

I found a forum message with diagrams for the German W28 (forum link).  I also compared the inside of the base of this phone with my FUSI No. 1 (forum link) and found that they are remarkably similar.  What is confusing me is that the Tesla came to me with a three-conductor handset cord and a handset which appears to have been designed for three wires, but the FUSI phone and the W28 diagrams have four wires for the handset.  The handset cord on my Tesla is obviously not original, but the handset does have the Tesla logo moulded into it.  This phone came from the same collection as my Swiss Autophon phone (forum link) which had the wrong dial on it, so it is conceivable that whoever collected these did something weird with the handset on this phone.  I can probably borrow a WE 500 type four-wire handset cord to use on this phone for the present.

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #4 on: May 07, 2014, 02:43:50 PM »
Larry, I do not have a schematic for this particular type. It seems to be different from the W28's that I have, in that it does not have a seperate connectio for the ringer, near where the cords enter the phone. I'll take a pic later. It happens that I am working on a W28 at the moment.

The brochure that Paul F gave the link for says the cord should be 4 wire (4 way the brochure says). And braided, according to the pic provided.

I know this type of handset very well from other types of phones. Normally they allow both 4 and 3 wire cords. Do you have pics for the wiring inside?

I have a Tesla intercom with the exact same handset. It has a 4 wire braided cord. (NOS, by the way. :-)
Groeten,

Arwin

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And I am on facebook too: www.facebook.com/matilosvintagetelephones

Offline LarryInMichigan

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Re: Tesla Phone
« Reply #5 on: May 07, 2014, 02:57:14 PM »
I have seen the braided four-wire German handset cords, but I do not have any.  In this handset, there are only two screws in the side where the cord enters.  The white wire in the cord extends all the way to the receiver end, and there is a yellow wire which runs through the handset from the transmitter end to the receiver end.  This would connect to the common.  It could be that this receiver is not the original.  The yellow wire has vinyl insulation, so it is not from 1949.

If anyone has a proper four-wire braided cloth handset cord to spare, I would be interested.

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #6 on: May 07, 2014, 05:28:55 PM »
Now I look at the pic in the brochure better, I think it is not a braided cloth cord, but a braided plastic cord. German phones used to have those, in that periode around 1950.

When you take out the yellow wire, the handset becomes a 4 wire handset. It leaves you with 2 connectors for the transmitter and 2 for the receiver.

The Tesla intercom I have, turns out to have another model handset. See pics. Sorry.

I've made some pics of a Heemaf Type 1931, but it pretty generic for a W28. You can see the extra connections, marked W2 (w = wekker (ringer)). This way of wiring allowed easy connection of a 2nd ringer in series with the telephone.

There are 2 rows of cennecting points, in my case marked FFMM for the highest row and E b "blanc" a on the lowest.

FF is Fernsprecher (receiver) and MM is Microphone.

E is Earth, b tip "blanc"  = unused a = ring
« Last Edit: May 07, 2014, 05:34:58 PM by Matilo Telephones »
Groeten,

Arwin

Check out my telephone website: http://www.matilo.eu/?lang=en

And I am on facebook too: www.facebook.com/matilosvintagetelephones

Offline LarryInMichigan

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Re: Tesla Phone
« Reply #7 on: May 07, 2014, 06:52:28 PM »
My phone does not have the board with the terminals for the external ringer, but the metal bracket at the rear does have the two threaded holes to which the board on clamp would have been attached.  It could be that someone removed the parts at some point in the phone's history.

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #8 on: May 08, 2014, 03:26:44 AM »
Could be, but I see no loose wires.

Pity the diagram is missing.

These holes are also for a bracket that acts as a strain relief. See my picture for such a bracket.
Groeten,

Arwin

Check out my telephone website: http://www.matilo.eu/?lang=en

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Offline LarryInMichigan

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Re: Tesla Phone
« Reply #9 on: May 11, 2014, 10:13:23 AM »
After a few hours of struggling, I finally have the phone reassembled and working.  I used the W28 diagrams posted by dsk (forum link) as a reference.  The wiring on this phone is almost the same, except that the dial is a bit different, so one of the dial wires needed to connect to a different terminal to shunt the receiver.

For a couple of hours, I just could not get any sound out of the receiver, and the phone put too much of a load on the line when off-hook.  I finally discovered that one of the screws on the terminal strip was pinching one of the wires on the other side and causing an unwanted electrical connection.  At least part of the blame is on the two screws which were missing and therefore replaced with screws from a Swiss parts phone and which were longer than the originals.  Once I fixed that problem, I found another intermittent short which sometimes bypassed the transmitter.  Everything seems to be in the right place now, but the transmitter sounds like a candlestick type, so I would like to replace it.  Neither the transmitter nor receiver have the Tesla name or logo on them, and the receiver has some cyrillic text printed on it.  I assume that they have both been replaced, possibly by a Czechoslovakian PTT technician.

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #10 on: May 11, 2014, 01:05:54 PM »
Good to hear that it is up and running.

As I have very very little experience with candlesticks, what do you meand when you say this phone sounds like one?
Groeten,

Arwin

Check out my telephone website: http://www.matilo.eu/?lang=en

And I am on facebook too: www.facebook.com/matilosvintagetelephones

Offline LarryInMichigan

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Re: Tesla Phone
« Reply #11 on: May 11, 2014, 01:08:25 PM »
From the transmitter, my voice sounds like I am speaking through a tin tube, similar to the way it sounds from a 1920s or earlier transmitter.

Larry

Offline Matilo Telephones

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Re: Tesla Phone
« Reply #12 on: May 11, 2014, 01:31:25 PM »
Hmmm, in a way that is kind of neat.

I have kept a transmitter that gives squeels, crackles and pops. It may come in handy sometimes.
Groeten,

Arwin

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Offline dsk

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Re: Tesla Phone
« Reply #13 on: May 11, 2014, 01:38:18 PM »
That sound are not uncommon on those handsets, If you put/hold that capsule in place and trying it in e.g. a W.E. 2500 it will give a better sound.  The shape of the bakelite may have a reason.
You could also unscrew the cap on your Tesla, and hold the transmitter in place and try speaking.

The depth of a W.E. transmitter may be to big to fit, the diameter are slightly smaller.

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Offline LarryInMichigan

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Re: Tesla Phone
« Reply #14 on: May 11, 2014, 06:09:46 PM »
I have other similar handsets which sound better.  I tried another transmitter in the handset, but it didn't sound much better.  I haven't yet tried this transmitter in another handset.

The receiver element has the lettering: "ктд-1" and "БдС" on it.  It looks like there was a "БдС" on the back of the transmitter, along with other things I cannot make out, as well.  Are they Soviet or Bulgarian?

Larry