Tesla desk phone -

[wds]

I picked up this Tesla - appears to be a brown color, but I haven't been able to figure out if it's brown or just a faded black.  I have read that this model Tesla  produced before the GPO 300 series, and GPO copied it?  Would like to know which came first.  I can't figure out how to  wire this phone to my telephone line.  The line cord has 4 wires, connected to terminals 1,3,5,7.  I tried a few variations but couldn't get it to work.  Does anyone know how to hook this phone up to the line?  Also, I need to take the fingerwheel off for cleaning - if I remove the small screw in the middle, and then the fingerwheel, do I need to worry about the spring popping out, or anything else that would ruin my weekend?

[LarryInMichigan]

So you're the one that got that phone.  I should have figured.

I expect that the phone is mostly based on Ericsson's design.  The screw in center of the finger wheel is certainly an Ericsson thing.  On most, if not all of these, the spring is held inside of a metal cup which needs to be rotated slightly before it will lift off of the center shaft, so there is usually no danger of the spring flying across the room as soon as the finger wheel is removed (for some reason, this always reminds me of the tacky 1970s peanut can gag with the spring snake which flies out when the cap is removed).

I would suggest looking at Ericsson wiring diagrams if there are no Tesla ones available.

Larry

[twocvbloke]

Definitely a spin-off of the Ericsson design, but whether it's wired up internally as per the various builds on the basic design, only pictures of the inside can tell...

[LarryInMichigan]

I doubt that the German style handset is correct for that phone. 

Larry

[rdelius]

Tesla was post WW2 after private companies were nationalised.Note 1947 date.Tesla did make that style handset ,Don't know if they were origionally togather.look for dates on the parts and the Tesla  logo

[wds]

Handset has Tesla receiver and transmitter elements, with the Tesla logo on the caps.  I'll check the dates tonight.  Here's a pic. of the inside - notice the 4 line cord wires (top row).  The wiring diagram shows the 4 line cords, but I'm having trouble figuring out what they go to.  Looks like #7 is ground, #3 & 5 are together.  So it's L1 = 1, L2 = 3,5,7 combined?  

On the screw that holds the fingerwheel - is there a correct tool to remove that screw with?  I went out and bought a snap ring tool that I think will work.  The 1/4" security spanner tool is a little too small.  Does anyone know if the correct tool can be purchased?

[twocvbloke]

Looks like Terminal 1 for one side of the line, join 3 and 5 together for the other side of the line, that "should" make it work if it's wired up correctly inside...

[wds]

What about 7?  Diagram shows it going to a switch, but I'm not sure what that switch is for.  could it be the button up by the handset?  do you know what that button is for?

[dsk]

About the design: http://tinyurl.com/pup84go
dsk

[twocvbloke]

What about 7?  Diagram shows it going to a switch, but I'm not sure what that switch is for.  could it be the button up by the handset?  do you know what that button is for?

That's just an earth-loop Recall switch, it's not used today, it was used on the old style shared lines we used over in this half of the world or on PABX/PAX systems, you can ignore it...

[wds]

Great, thanks.  I'll fire it up tonight.

[rdelius]

I do not think removing that disc with holes will remove the fingerwheel but will allow you to remove the disc from the fingerwheel. The fingerwheel has to be unclamped from the gearing inside if this dial is the same as the dials on some sealier Ericssion sets

[wds]

Thanks for the info on the dial.  I just removed the screw, and the fingerwheel is still on there pretty tight.  Also, there is a depression on the fingerwheel that bumps a notch on the blank number plate that stops the fingerwheel from turning.  There is definitely tension on the fingerwheel from the spring.  I cleaned it pretty well for now - I'm not ready to take the dial apart just yet.  I'll find another dial to practice on.  

The phone works now - terminal #1 is L1, crossing #3 & 5 allows the phone to work, and crossing #3, 5, &7 also allows the ringer to work.  The ringer seems to be on terminal #7.  

Also here is a picture of one of the caps - you can see the Tesla Logo - although it's a marked Tesla handset, I would look better with the other type.

[dsk]

If this Dial are like the older Ericsson dials, you have to remove the dial assembly from the phone.
When you have remove the hybrid and hook-switch assembly (a iron frame fixed with 2 bolts) you may see 2 other bolts or nuts under the dial, remove them, and pull the dial assembly out from the front of the phone. the dial mechanism are covered by a box, fixed by 3 screws around the outer edge, then you get into a mechanism not to different from an old A.E. dial. To remove the dial almost everything has to be taken apart, but it is a quit simple mechanism, actually so simple so the tuning of the rest position of the rotating bakelite plate may be essential, so take pictures before, and during dismantling.

dsk

PS My dial is made by the Norwegian Elektrisk Bureau, and are probably quite rare, but this photos arw the only I ones I have at this moment.
DS