New member -RTT56 sound issues

[floyd111]

Oops.. not a good start. I think I posted my thing in the wrong thread. My apologies for he double post.
OK, let's try this again..

My name is Stan and I am a Dutchman living in Taiwan.
I could sure use some help solving some technical issues.. I am not an electrician at all and can not read a wiring diagram, except for the basic colors, wires, connected to the right poles.

I bought a Belgian copper RTT56 dial phone at an auction and I adapted it to work with the modern land lines. That was easy.
Everything works, it rings, dials out and what not.
However, I needed to replaced the horn-cord, and I did. The phone worked better than before, no more cracking sounds.
Outgoing volume is loud.

One issue remains. Incoming sound is very poor. No static, no hissing, no disturbing noises.. just very low volume.
I have 2 explanations, but both may be rubbish.
- the old dial phones need more electricity than is supplied on modern landlines. I remember getting shocks from naked telephone lines when I was a kid. No shocks today. So, I need to increase electricity through a charger of some sort, to feed the amplifier in the phone.
- The cable I used to replaced the horn cord was a computer cable, the one that goes from the electricity socket to the computer. This cable is too thick, and reduces volume

Are these explanations nonsense? Can anyone tell me how to increase incoming volume?

I cleaned the contacts in the horn. Nothing wrong there but a little oxidation. Issue remains after cleaning.
I checked the horn. Both sender and receiver are original, with Proprietee de l'etat" (government property) written on it.
Clearly Belgian gov stuff.
So.. what to do?

Thanks so much!
Stan

[Matilo Telephones]

Hi Stan,

Was the outgoing sound (transmission) louder, before you changed the cord?

If not, the usual problem is that the sound level microphone (transmitter) goes down as it gets older. This is a very common problem. Changing the transmitter for a better one is the most used solution.

By the way, Proprietee de l'état is specific to French telephones. The RTT 56 was originally painted black, over its zamac body shell. The fact that it is copper now and that it has a French handset, means it has had a make over. The paint was stripped and it received a copper plating and was put back together.
Reassembly was often very crudely done, and parts got mixed up. Damagaded handsets were replaced with whatever handset they had. So you can find French, Dutch and even German handset on these pimped up RTT 56s.

Groetjes van een andere Nederlander. :-)

[Jack Ryan]

Was the outgoing sound (transmission) louder, before you changed the cord?

If not, the usual problem is that the sound level microphone (transmitter) goes down as it gets older. This is a very common problem. Changing the transmitter for a better one is the most used solution.

I think Stan is saying that the receiver is quiet, not the transmitter. It might be that the receiver is OK but that the French receiver is the wrong impedance for the Belgian circuit. Arwin?

Regards
Jack

[Matilo Telephones]

Sorry. you're right. I'll have another coffee.

I'll check for these impedance values tonight.

[dsk]

Hi, and welcome.
It may be the receiver element, (loudspeaker) in the handset.  A simple test could bee to connect the receiver direct to the line, and just listen if the dial tone is considerably louder.  If yes the error will probably be somewhere else.
And remember this circuit has an anti sidetone compensation, so you should hear yourselves weaker than the other end will.

dsk

[rdelius]

If that state property handset  came of a U42 set,the receiver capsule might need a DC bias not found in telephones with modern circuits

[floyd111]

Well, it sure seems an RTT56 to me, and the Belgians are bi-lingual, remember?
The full copper RTT is a known model and I understand it was first made available to Belgian ranking gov officials, before it went public. There are registered RTT56's, stamped as early as 1948, (I learned online) where the public did not get those until the early 50's
The internals on MY phone are stamped RTT56, and the handset has the same writing on the grip, as well as on the mic and speaker.
Bottom plate also has the stamp. Internally, on the wiring diagram it is stamped RK, and the wiring diagram is bi-lingual. Belgian.
On the internal plate it is stamped 1965B, which looks like the MY

I can't say whether the sound was louder before I changed the line. Too much distortion before the repairs.

If the receiver goes bad, I learned that there will be all kinds of issues, but "low volume ONLY" was not among the descriptions I found online. Always a combi with hissing or cracking sound, or no sound at all.

I hear myself very clear and pretty loud through the phone. Does that mean anything?

[LarryInMichigan]

I also bought a Belgian RTT-56 which had a French handset on it: forum link.  I eventually bought another RTT-56 and combined the parts from the two to make one good phone with the correct handset.  I moved the handset to my French U43 because its bakelite finish was much better than the handset which came with it.

Larry

[LarryInMichigan]

Here is another post about another one of these phones which had a French handset on it: forum link. 

Larry

[unbeldi]

and the wiring diagram is bi-lingual. Belgian.

Belgian?   where do they speak that?

[Matilo Telephones]

Well, it sure seems an RTT56 to me, and the Belgians are bi-lingual, remember?
The full copper RTT is a known model and I understand it was first made available to Belgian ranking gov officials, before it went public. There are registered RTT56's, stamped as early as 1948, (I learned online) where the public did not get those until the early 50's
The internals on MY phone are stamped RTT56, and the handset has the same writing on the grip, as well as on the mic and speaker.
Bottom plate also has the stamp. Internally, on the wiring diagram it is stamped RK, and the wiring diagram is bi-lingual. Belgian.
On the internal plate it is stamped 1965B, which looks like the MY

I can't say whether the sound was louder before I changed the line. Too much distortion before the repairs.

If the receiver goes bad, I learned that there will be all kinds of issues, but "low volume ONLY" was not among the descriptions I found online. Always a combi with hissing or cracking sound, or no sound at all.

I hear myself very clear and pretty loud through the phone. Does that mean anything?

Bilingual indeed. Stricktly bilingual, especially back then. For a text on an official goverment issue item to appear only in French would be an affront to the Flemish and would be vehemently protested. You will find that all RTT expressions will always be in both French and Dutch.

The RTT 56 was introduced in 1956, hence the 56 in its type designation. I have never seen an original copper one and I have seen and opened up quite a few.
You will invariably find remains of the original black paint inside and if you scrape away a little of it, you will find bare zamac under it. This shows that the phone was originally zamac (a zinc alloy), that was painted black which was afterwards removed and the copper plating applied.

I do not know what you mean by registered RTT 56 from 1948, but a copper one to appear 8 years before its offcial introduction seems highly unlikely to me.

There is a lot of stuff on line on these phones that is simply incorrect or exaggerated, mainly by sellers who want their item seem more interesting and older than it really is.

There is however an earlier version of the RTT 56, only made by ATEA, called the Ateaphone 50. It was develeped in the late 30s and is very similar to the RTT 56.
It was also used by the RTT, but also sold for private installation. It differs from the RTT 56 mainly (if it is an original one) by the absence of the carrying bracket, the absence of the RTT shield at the front (and no rivet holes for it) and the big earthing button, compared to the small white earthing button you find on RTT 56s.
And of course the Ateaphone has the hambone type handset, typical for Atea telephones. The RTT 56 (an original one) should have a F1-like handset.

Please find attached a diagram and drawing of a manual from RTT containing diagrams of all their telephone equipment from 1955. It is from the earlier Ateaphone. The RTT 56 version is absent from this manual.

Please note that even the word metal is in both languages.

Perhaps you can show us some pictures of your telephone, so we can establish what it is exactly and perhaps a picture of the markings on your loudspeaker?

[floyd111]

Your ATEA story sounds very much like what I heard. Indeed, it was not called a 56, but it was called an RTT.
Still, it's not about dwelling in history details for me, for I am not a collector, nor a specialist. I just loved this phone and bought it. Only found out details long after I was already using it. The internals being stamped 1965B, is a more important given here, I think.
Just took out a big knife an cut a chunk out of the of the copper casing, along the bottom edge. It's copper, through and through. No coating.

My dial card is missing, but also the little RTT seal in front. I have 2 tiny screw holes there, where it once sat.
You think I could find either of them somewhere?

The RTT stamp on the bottom plate is clearly visible.
Less visible is the "A" that was partially rubbed off during the years.
Guess I have an 1965 RTT 56A. Does that stroke with the internal stamp "1965B"?
here's a few more of these phones:

http://page18.auctions.yahoo.co.jp/jp/auction/w127066084

http://www.ebay.de/itm/Wunderschoenes-altes-Telefon-Kupfer-Bakelit-Kupferummantelung-RTT-56-A-RARITAT-/110966882070

https://www.google.com.tw/search?biw=1280&bih=658&tbm=isch&sa=1&q=RTT+56A&oq=RTT+56A&gs_l=img.12...460075.460075.0.461327.1.1.0.0.0.0.38.38.1.1.0....0...1c.2.64.img..0.0.0.gwRnO5Hvthg#imgrc=E4feyoS3B81PNM%3A

[floyd111]

Looks like the horn-type changed early 1960. Mine is not the same as the early horns.
Regrettably it also does not look like I have the later one, haha! The other late models I see have a rounded version.
Mine is fin-shaped. Guess that my "Proprietee de L'etat" horn may be French after all.
Can anyone tell me whether there are RTT's with that French marker?

[Matilo Telephones]

Well the RTT 56 was made by 2 manufaturers. ATEA, the RTT 56 A and BTMC, the RTT 56 B

The parts on your phone marked A are made by ATEA and the ones marked B are made by BTMC.

Your dial seems to be an ATEA dail.

Your first link leads to one not with a french handset but with a BTMC handset, that also is not original to the RTT 56.

The second link does show one with the original F1 style handset.