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Tesla T58 "horseshoe"

Started by countryman, August 19, 2019, 03:02:28 PM

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countryman

Out of curiosity for the design I bought a czechoslovakian Tesla T58.
Even finding it's correct name wasn't easy. This model seemingly was not too common ouside Czechoslovakia. My individual one is from bavaria, how it got there is unknown.
Finally I found the czech site http://miltikablog.cz/telefonni-pristroj-tesla-t58/ With the help of google's translation service I learned that it was the only bakelite phone designed and produced by Tesla. The czechoslovakian Tesla brand arose out of forerunners in 1946 as a state-owned monopoly electronics manufacturer. It's earlier phones were designs from former independent companies that went up in the monopoly, it's later phones were made out of thermoplastics.
The production site of my phone in Liptovsky Hradok is now re-privatized and still produces telecom items (Teslalh.eu)!
The T58 can't hide it's Siemens & Halske roots (S&H licensed several productions of independent manufacturers in CZ before WWII): Circuitry,  the dial, handset cap threads, receiver design... are all similar to S&H phones (only the A...R letters are CZ specific).
Yet the design is unique: It's leading over from classic bakelite concepts to the rounded design of so many later european almost indistinguishable plastic phones: The Grey Mice. The T58 was definately trendsetter!
While the T57 has a classic, conservative interior as seen in this thread:
http://www.classicrotaryphones.com/forum/index.php?topic=9762.msg230153#new
the T58 is almost identic on the outside but surprisingly innovative when opened up: The terminals, capacitor and induction coil are one single monolithic  unit molded into a bakelite (?) part. That must have been revolutionary in Europe, but later models went to printed circuits quickly.
The shell has a recess for an earting button like in the diagram, which my set does not have, but a filling piece instead.
The phone arrived nasty and once again a previous owner must have been a heavy smoker  :o After cleaning the surface was matt and some parts even grey from the bakelite filler material showing through. I used a black pigmented polish to correct that and I'm happy with the result. The shell has minor chips at the bottom which don't bother me and the phone is in good working order.

countryman

2 more pics:
Inside the dial there was a small paper slip. Unfolded, it seems to be a test diagram of the dial from the day of production! The upper blue line shows 10 pulses. Never seen that before...

LarryInMichigan

I have seen those dial pulse graph slips on the dials on several of my phones from the socialist countries.  I think that Tesla had the highest quality phones in the Soviet bloc.

Larry

Jack Ryan

Quote from: countryman on August 19, 2019, 03:05:58 PM
2 more pics:
Inside the dial there was a small paper slip. Unfolded, it seems to be a test diagram of the dial from the day of production! The upper blue line shows 10 pulses. Never seen that before...

That's interesting because I usually find the graph in German telephones.

It's also interesting that the circuit diagram is drawn "backwards" as the GPO did with the line terminals on the right.

Jack

tubaman

Quote from: Jack Ryan on August 19, 2019, 08:41:50 PM
...
It's also interesting that the circuit diagram is drawn "backwards" as the GPO did with the line terminals on the right.

Jack

I think you'll find that it is the right way around and it's all the others that are backwards.  ;)

@countryman - that's a nice phone and has cleaned-up well.
It's a model I'd like to have but most I see seem to be damaged more than just a few minor chips.
:)

countryman

Quote from: countryman on August 19, 2019, 03:02:28 PM

The phone arrived nasty and once again a previous owner must have been a heavy smoker  :o

Thinking it over, most bakelite parts that I cleaned leached out a brownish substance which I used to consider tobacco fumes. The longer I think about it, it must be from the bakelite itself, maybe decayed phenolic bonding material from the surface?
Bakelite is stable against many strong solvents, and all I use is window cleaner and in one case denatured alcohol. So I don't think my operations corroded the bakelite, but only removed already decomposed surface particles? More so, as extended scrubbing and washing does not dissolve additional brownish stuff any more.
Just a thought...

HarrySmith

I have noticed the same thing with bakelite. Always turns the rags brown no matter how many times I clean it. I usually use either window cleaner or Oxi-Clean. Trying to buff them after cleaning still produces the brown stuff.
Harry Smith
ATCA 4434
TCI

"There is no try,
there is only
do or do not"