Restoring an RTT 56

RTT 56 before
RTT 56 before

This is the telephone type I get the most questions about, by far. And not only from the Netherlands and Belgium, but from all over the world.
As I was going to restore one for a client in Belgium, I thought it would be good to write up a restoration report about it.
Restoration can mean many things and for every telephone collector it means something else. In this case it means cleaning and polishing, replacing missing parts and giving it a tune up. It does not need much else, as the phone is in good condition and undamaged.
I usually try to keep all the original parts together, as not to lose any of its history. I also do not reverse all forms of wear, as it gives character to an old phone opposed to damage, even if it does not affect the functioning of the telephone.
And last but not least I do not like to restore it beyond factory original: it must not look better than how it looked when it left the factory.
Interestingly in this case we have a painted metal phone, so it needs to be treated a little differently as a bakelite or plastic telephone.

But first I recommend you read my article on the RTT 56 A and RTT 56 B.

Preliminary survey & opening it up

Before starting a restoration I check the telephone and take stock of what needs to be done. Other than the obvious cleaning and polishing I may need to replace parts and repair damage and I like to get a good idea of what I am going to need to do before I start.
Besides that the client has asked me to replace the curled handset cord with a cloth covered one.
The first things to correct are rather obvious: the dial label with plastic cover is missing, as its retaining ring. And the original screws that hold the bottom cover have been replaced too.

RTT 56 opening it up
RTT 56 opening it up

Unfortunately I do not have a spare retaining clip and no spare screws. So I need to find a solution for that. I will try to find such a clip, but if I cannot find one I may need to replace the dial entirely for a different model, which was also used by RTT.

The housing opens by undoing the 2 screws at the bottom. The bottom plate just slides off. Please mind that you do not have to undo the 2 screws entirely.

Inside there is not much wrong with this telephone. Everything seems to be there and no other parts missing. The paint is in reasonably good condition, as are the bakelite parts. So no really difficult repairs, or so it seems.
But often after cleaning surprises with regards to repair jobs may emerge.

Testing & repair: somebody has been tinkering with the dail

I cannot say this often enough: first test if your phone actually works, before restoring. Restoring it won’t make it work. If it does not work, you will need to repair it first. This may mean just replacing parts, but often it means making parts or adjusting existing parts.
All too often I am contacted by somebody attempting a restoration, only to find halfway through the process that the phone they are working on doesn’t actually work!

RTT 56 cam wrong
RTT 56 cam wrong

In this case the phone did not work properly. There was a problem with the dial, the cam wheel was for some reason put on upside down. Why this was, is unclear. Apparently somebody tinkered with it and did not know how to put it back together again. Perhaps this has something to do with the missing dial label and retaining clip.
Things like this may indicate there are more things wrong with the phone, as the tinkerer may have been tinkering with other parts of the phone. In this case I could not find any other problems with the phone, so after repairing the dial it worked fine.

RTT 56 cam correct
RTT 56 cam correct

In any case this inverted cam wheel illustrate that you can find the strangest things wrong with a phone and any results of tinkering, botching and snafu-ing may not be as obvious as you may think. So beware.

We do need to test the phone again after restoration and I will probably adjust the dial speed for optimal operation.
And please note that we may replace the dial, so we need to test the phone with the replacement dial too if I cannot find a clip for the dial label.

Disassemble, wash and clean: metal needs to be treated differently

Picture taken before removing wires
Picture taken before removing wires

When disassembling please mind that you take pictures. You will need these as a reference when you put it back together again. I do this too, especially with telephone models I am not familiar with.
Some telephone diagrams are hard to read, so some kind of record as to which wire goes where is also highly recommended. I often make notes on paper, aside from taking pictures, on the wiring and a to do list of the little jobs I need to do on the phone in question.
Disassembling an RTT 56 is reasonably straight forward. After opening, undo the screws of the subframe, undo the wires (take pictures!) and remove the dial. Unscrew the caps of the handset and undo the handset cord.

CAUTION!  SOME HANDSETS HAVE A BLOCKING MECHANISM!

RTT 56 cap unlock
RTT 56 cap unlock

You nead to insert a pin in a hole on the rim of the transmitter cap, to be able to unscrew it.

In this case we have a metal phone with a bakelite handset. Bakelite can be washed easily, so after you have removed the cord, transmitter and receiver, you can chuck the bakelite parts in luke warm water with washing up liquid. Scrub them down well with an old tooth brush, because there is a build-up of all grime and gunk that is decades old. Do not forget the sound holes in the transmitter and receiver cap.
The metal bits on the outside are a different story. I do not like to immerse painted metal parts in water, as it that can seriously damage the paint. It may stain the paint and water softens the paint too, risking damage.
I usually wash painted parts by  wiping them down with a window cleaner called Glassex. I use a sponge and lots of tissue paper.
For the nooks and crannies I use a moistened tooth brush and wooden tooth picks.
The inside I brush with a dry brush to remove all the dust. On the base plate the dust has caked so it is not easy to remove. For that I used a moistened tissue, but I was careful to avoid the paper diagram.
This telephone was fairly clean inside. If there is more dirt or if there is rust, more rigorous cleaning techniques may be required.
Luckily the insides of RTT 56s tend to be reasonably clean, especially the upper compartment.

RTT 56 plunger
RTT 56 plunger

One problem with the RTT 56 is that they used a piece of wire to secure the cradle plunger and the carrying bracket. See picture.
If you bend this wire, it will break and I do not have a good source for replacement wire. Therefore I left these parts in place and cleaned them in situ. This did not make it easier to clean the housing with the bakelite plunger.
The plunger itself is made of bakelite, but can be polished the same way as the painted metal housing. Please mind there are lots of corners and edges on, around and under the plunger. So the toothbrush is vital for cleaning this. Here I also used glassex to get it properly clean.

Polishing

RTT 56 polishing body shell
RTT 56 polishing body shell

The bakelite parts, which are only of the handset, I have polished with my Dremel. Afterwards I buffed them a little more with a dry cotton cloth.
The metal parts, such as the housing, carrying bracket and finger wheel, I lightly hand polished with the same compound as I used for polishing the bakelite. That is quite enough in this case, as the paint is in good condition. Please do not polish painted metal parts with the Dremel. It will get too hot and melt and burn the paint.

RTT 56 bottom polished half
RTT 56 bottom polished half

After cleaning, I polish the painted metal with a compound called Commandant no 4, using a dry cotton cloth. Commandant no 4 is silicone free and contains very little solvents. It basically consists of a fine polishing powder and a soapy substance, but no wax.

The dial

This particular specimen has a BTMC dial. If you remove the finger wheel, the spring will unwind. And you do not want to unwind the spring. See this article for more information about that.
In this case the dial is in good condition (even though I had to repair it, as I described above), so total disassembly is not required.

BTMC dial cleaned and installed
BTMC dial cleaned and installed

So I brushed the mechanism clean and used a tooth pick to clean all the gunk off the mechanism as illustrated in the same article.
In this case I removed the pile with contact springs, to give the gears a good brush. The pile is fastened with 2 copper screws. Be careful with replacing those, as they cross thread easily!

I cleaned the number ring as best I could, without removing the finger wheel. I did this by brushing first, occasionally turning the wheel a bit to get at covered parts. Then I used a tissue, that I moistened with glassex again. By pushing it through one of the finger holes and turning the finger wheel, I basically wiped the number ring clean.
I did this with both the first and last hole, to clean the hole number ring.
I ran a toothpick around the outer and inner edge of the finger wheel to get it really clean. I finished by giving the finger wheel a polish, after that had been cleaned too. Do not forget to clean the finger holes, as dirt tends to build up there. And of course the finger stop needs similar attention.

Replace or order part?

Well, cleaning and polishing did not make that problem with the missing retaining clip for the dial label go away. I searched my stock of spare parts, but I did not have a spare.

BTMC dial with number card
BTMC dial with number card

Making a new one is not that easy. The original part has a rectangular cross section. It is not round. That is because it is made to fit in a groove in the finger wheel. I could make one from round wire, but chances are it will not fit properly inside that groove.
I talked to the owner of the phone about it and suggested replacing the dial, as I had a dial made by ATEA, the same that can be found on the ATEAPHONE.
But the problem with that dial was that the mounting holes were spaced differently so it could not be mounted in the shell without modification.
So I started fabricating an adapter ring when a donor phone came into my possession so I could complete the original dial, with a nice dial label too!
Nevertheless it touches upon the question whether to replace or to get a new part. In this case I could perhaps have gotten a GPO spring clip (these are sold on line), and adapted it to fit. Not sure how that would have looked.
Making a replacement part or adapting an existing part may not look quite right, depending on your fabrication skills and equipment. And it takes away from the telephone’s originality.
Leaving out a missing part on the other hand often looks terrible. So deciding what to do can be a real dilemma.
Whatever I do, I always try my best to keep the changes I make reversible. In that case I can always undo what I did or, even better, I can always upgrade my repair to a better quality, for instance when I find that original replacement part.

Cords

RTT 56 rear with cords
RTT 56 rear with cords

Even though the original curly cord is in good condition, the customer wanted a cloth covered handset cord. So I replaced it. I used a reproduction cord with red, blue and yellow wires. These are the colours used here in the Netherlands. I do not have any other colours in stock. Original Belgian colours would have been red, blue and black. Fortunately once mounted, you cannot tell the difference.
For the line cord I reused the cord that came with the phone. I did not have an original Belgian cord to replace it.

Old and new Belgian plug
Old and new Belgian plug

 

 

I did however have to rework the ends. I cut of a little off the ends, stripped and put new spade connectors on.
I also replaced the plug. The old one was cracked, probably because somebody stepped on it.

Luckily I had a spare Belgian plug. I did put on a strain relief to fit the plug. After all the telephone is meant to be used on a daily basis, so any repair must be quite durable.

Green goo

Green sticky Belgian goo
Green sticky Belgian goo

Not for the first time I found that the Belgian line cords seem to leak a greenish goo from the ends. I seems from the inner wires, where the isolation has been stripped of. It is translucent, sticky and similar to ball point ink, except it can be wiped off easily.
I am not sure what it is. It could be softening agents from the isolation, but the strange thing is that it comes from the inner wires only. Perhaps the green colour is from the copper from the wires themselves, although copper compounds usually have a lighter colour green.
So as the wires seem unaffected I left them on.
I did however enquire with my Belgian telephone friends if they knew anything about this phenomenon.

Converter

Converter installed
Converter installed

As my client wanted to use the telephone on a daily basis, he specified to have a converter built in. I will not cover the whole process of building in a converter like this in this article. It would take too long. In the future I will publish a separate article on how to install one of these.
The convertor used is a picbasic convertor made by Frits Kieftenbelt, here in the Netherlands.
Please mind that I fitted the convertor wires with spades, that match those that were used on the rest of the phone. I also added a terminal strip. It this way the telephone can be returned to its original state, with any cutting, soldering or otherwise altering the phone.
I also did my best to tuck away the wiring neatly and to secure the extra terminal block and the convertor to the inside.

End result

RTT 56 after restoration
RTT 56 after restoration

So here it is, nice and shiny, fully functional and compatible with the modern telephone network. Good for another couple of decades. My client was happy with it and consequently so am I.

 

5 Comments

  1. Sevus Arwin,
    Als kleine -letterlijk 🙂 – kleine verzamelaar/ knutselaar, wonende aan de Mosel in DE, geniet ik enorm van alles wat ik vind op internet van jou.
    Veel dingen zou ik graag bij een “bakkie doen” met je hebben ovetlegt.
    Hier in R.P. DE ben geb ik nog geen ander met deze hobby gefonden.
    Mijn kleine collectie gaat van de Eriksson 1902 – met originele batterijen – via o.a. een eriksson “kleppenkast” 10 lijnen 1905 centrale – tot gisteren binnen gekomen originele T&T payphone 1952 en andere curiositeiten (Bear o Fone 🙂 en alles wat ik maar hier (in redelijke staat) op vlomarkten tegenkwam (bv een RTT zoals jij in de restaurering anleitung omschreef, die dus goed van pas kwam 🙂 Sommigen willen series kompleet hebben, mijn beste ega ter wereld laat dat niet toe, ze leefd nu al in een soort techniek museumpje 🙂
    Als ik in NL kom wil ik je graag bezoeken, een soort bedevaartreis dus 🙂 🙂
    P.S. mijn hobby is begonnen 60 jaar geleden samen met Appie Doornenal (nu Expert) uit Nijverdal, aan de Bergleidingweg, door het wel 1250 mtr ver uit elkaar aansluiten van twee militaire veldtelefonen (de mijne heb ik NU nog!) en ik leerde o.a. dat je van de inductor een beste opn… kon krijgen.
    Laat het rinkelen!
    Moselgroet.

    • Hallo Ian,
      Bedankt voor je enthousiaste reactie. Altijd leuk te vernemen dat iemand geniet van mijn website en er iets aan gehad heeft.
      KLinkt als een leuke collectie. Ik zal je ook even een email sturen. Wellicht vind je het leuk om wat foto’s aan me te sturen.
      Mocht je in de buurt zijn, ben je altijd welkom voor een bakkie koffie. 🙂
      Ik ben zelf wel eens bij je in de buurt geweest en heb daar zelfs een telefoon op de kop getikt. Mijn KFeApp 385 heb ik letterlijk aan de oever van de moezel gekocht, in Zell.
      http://www.matilo.eu/3-the-phones/1975-1990-druktoetsperiode/hagenuk-kfeap-385-berlin/?lang=en
      Ik mag overigens van mijn vrouw ook niet mijn telefoons overal neerzetten hoor. De meesten staan op mijn zolderkamer. 🙂
      Groeten,
      Arwin

Leave a Reply

Your email address will not be published.


*