Restoring an Ericsson type 1951

rest 51 voor
Before
rest 51 9 klaar
After

This is an Ericsson type 1951 made for PTT. I will explain step by step what I did to give this telephone a step by step basic restauration.

 

This phone is dirty, used and has been stored for quite a few years. Beneath the dirt is a glimmer of promise. Bakelite looks fine. And it is in one piece, with at first sight no parts needing replacement. Dial sounds like a coffee grinder though.

Visual inspection and technical check

rest 51 zijkantFirst I inspected the phone visually. Everything seem complete with no broken parts. So, probably it will work. There is very little rust. It is awefully dusty, but that can be remedied.

All parts are original to this type of phone. Often the handset is replaced with a different type and make, but this is not the case now. As you can see the inside is neat and tidy and only very dusty.

All the wires are bound together with little threads to form a loom. rest 51 openThey are solid core threads, that is bent through and between the different components. It gives it a nice and clean look. Most of the components are fastened with screws. That eases restauration. No plastic clips, bending wires, hooks etc.

Now comes the first technical stage. I like to make sure the phone actually works, before I start restoring. After reassembly I’ll have to check if the phone still works. That is the second technical stage.

I hooked the phone up to my test exchange. It rings fine, dials OK. Receiver and transmitter are fine too. Good, no problems sofar. Even the handset cord seems in good nick. Dial sounds very dry and noisy. If I need to replace dials or other technical parts I try to test them with the phone at this stage. There is no sense in restoring a telephone that isn’t going to work, after all.

Cleaning and washing

rest 51 2 wassenrest 51 2 wassen 2I cleaned the phone with washing up liquid and warm water. That is enough for most of the dirt and stains. Most wall paint comes of.

I use an old medium tooth brush for al the nooks and crannies. In this case the holes in the end caps of the handset. Give them a really good brush! Also the ridges of the logo on the handset. And the around the pins of the hookswitch. There is usually some kind of layer there of dunnowhatanddon’twannaknow.

Please do not use the abbrasive part of the sponge on bakelite. It scratches the surface.

The soft part of the sponge works wel enough for cleaning bakelite.

rest 51 3 schemaI also run the curly handset cord throught the folded sponge a couple of times to clean the curls really well. Don’t stretch it too hard.

There was also a sticker on the front of the phone. Had been there for decades. Because of difference in the aging of the surface, there is a shade where the sticker once was.

Inside the phone there usually is a schematic. It is hard to remove and easily torn if you want to remove it without wetting it. So I usually leave it on when washing. It either stays on or it comes loose during the proces. I just glue it back, when needed. The glue that was used based on gum arabic. I cannot seem to find such a glue at the moment. I now use a water based starch like glue. Like wall paste.

rest 51 2 labelI did keep the number card. The dirty and a little deformed plastic window too. It’ll clean up nicely and will give a bit of character to the phone. If the number card is unusable, I usually put in  a printed label with makers logo and type discription. I use a typewriter font for that, to give it a retro look.

 

rest 51 2 kapot snoerUnfortunately cleaning revealed that the handset cord is broken. I do not know a way to repair this in such a way, that the phone can be used on a daily basis. It will need to be replaced.

 

 

The really fun bit: refurbishing the dial

rest 51 2 draaischijfI really enjoy this bit (some other collectors hate this). Especially if there is a little thing wrong with the deal or if I am able to do some smart repair or something.

This time it is only a matter of cleaning and hoping the scraping/grinding sound goes away and it sounds nice and smooth again. And of course that it functions faultlessly.

I removed the bakelite upper parts. I dusted and brushed this part vigorously with an old toothbrush. It came out nicely.rest 51 4 draaischijf

Please note that I put the 2 mounting screws for the bakelite cover back, as not to lose them.

Be carefull with this particular dial. Underneath the metal cap on top is the leafspring. That cap that holds it is lose. It comes off if you are not carefull. The spring will fly through the room one way, the cap the other. This can lead to a lot of searching and putting it all back is a PITA. And you’ll need to recalibrate your dial.

So keep your finger on the cap when brushing or put the black retaining bolt for the fingerwheel back, while cleaning.

rest 51 4 draaischijf 2You can remove that crescent shaped bracket and remove the gouvernor (brass part) and the other gear. Make sure that you remember the position of the white plastic three winged disk, as you’ll have to put it back in the same position. Make sure it is turned clockwise fully untill it stops. Then position it as in the picture.

 

Please note that on this type of dial, the spring does not unwind if you remove these parts. On other types this might not be the case. So be carefull. Do not remove parts if you’re not sure. If the dial works fine there is no need to take it apart. Just brush and oil very lightly in certain places.

I brushed the gear teeth clean and also cleaned the axle holes with a toothpick. I wiped the outside of the governor with a dry paper towel. I wiped the inside of the brass governor housing with a dry paper towel too. The dirt in this part is what caused most of the scraping sound.

rest 51 4 draaischijf 3Just oil the ends of the axles marked with the green circles. Do not oil the governor itself. It is a friction brake that activates by centrifugal force. The faster it spins, the harder it breaks. And so regulates the speed of the dial. If you oil it, it won’t break well and your dial’s pulse timing will be off. I put a little drop of oil at the end of the leafspring. That is just visible sticking out of the end cap. The oil wil creap along the spring in time and will ensure smooth unwinding.

rest 51 6 stof 3I cleaned the contacts of the dial by brushing them with an old toothbrush. Ran a piece of paper between all the contacts. Paper is very abrasive so rubbing a contact with it cleans it up very nicely. It did the same with the contacts of the hookswitch.

Then I put everything together again. It works fine and sounds like new again.

You can see in the background a vintage screwdriver with a wooden handle. A while ago I bought a set of these for only a couple of euro’s. I machined them to my own desired width and size. Modern screwdrivers tend to be too thick for these old screws and leave toolmarks. I hate that and try to avoid that.

Polishing and dusting

rest 51 5 poets 1First the sticker. Removed the last bits of the glue with wasbenzine (lit: washing gasoline). It is a local product, difficult to translate. Nafta / white gas. Not petroleum or kerosine. Not terpentine. It is a milder solvent.

Anyway, acetone would have worked too on this. (Do not use on other plastics! They will disolve).

rest 51 5 poets 2Unfortunately the sticker leaves a dark shade. The bakelite not covered by the sticker has faded a little. That sticker has been there for decades. Top tip: avoid buying phones with old stickers, unles you want te leave the sticker in place.

After polishing it is only visible under certain angles and lighting conditions. rest 51 5 poets 3

I polished with Valma scratch remover first. On rough and dull parts I did that twice. U used a dremel on lowest speed. I often use Commandant no 4 polish, if the phone is less scratched to begin with.

 

I finished with Brasso copper polish. Aplied it with kitchen towel and polished with circular motion. Then let it dry and polishe again with a dry kitchen towel. Then buffed it up with a cotton cloth.

There are other ways to do this. Please note that I cannot use a bench grinder in my attick room, because of the noise. I work late at night. 2 small children, you get the picture.

I polished the other bakelite parts in the same way.

rest 51 6 stof 2rest 51 6 stof 1Next phase, cleaning the inside. Still reasonably basic. Used a soft paintbrush, an old toothbrush (medium), some paper towel, and a piece of paper. Brushed everything, thoroughly and removed the dust. Even brushed the wiring loom with the toothbrush. I also ran a folded piece of paper between the leaf spring contacts, to clean those (after brushing them). I also did that to the contacts on the dial. You could remove the bells and clean them. These are painted black, so a clean is enough to make them shine again. Bare metal ones may need polishing. I didn’t remove the bells in this case. It is a basic Rest 51 achterkantrestoration. This phone is not in pristine condition anyway. The back plate has some rust that will not go away easily and I will not respray it. That will lose the original lettering at the back (production date). Also the different electrical components are soldered to the loom and not removable idividually. I’d have to solder the lose. Also I could undo all the screws and lift off all the electrics in one go. IMHO this phone does not warrant such thoroughness, as it is not rare or pristine. That would be too much work.

 

Assembly

rest 51 7 draaischijfrest 51 7 draaischijf 3Well, almost everything is clean now, so time for some re-assembly. First the dial. Please note that not all the parts are made of bakelite. That means in most cases it is very unwise to put a Dremel to them, even at the lowest speed. Here we have some painted metal parst: finger stop and the bolt for the finger wheel. That is where my magic cloth comes in. It is a rag that I use for applying different polishing agents. Through the years it has become  rest 51 7 draaischijf 2impregnated with polishing powder. So rubbing with this cloth is often enough to make thing shine. It this case, with small parts, I fold the cloth a few times. Smooth it down on my work bench and rub the desired item over it. Workts great.

I have a special tool for tightening the bolt on the dial. It has 2 metal prongs that fit exactly in the holes.

Next, number card window. rest 51 7 glassexThe frame of this window is also not bakelite. Not sure what plastic it is. It is softer than bakelite. And it melts easily. Be careful! Gave it the magic cloth treatment. Also I cleaned the original transparent plastic window. It has yellowed over the years and has gone a bit wobbly. Great! Gives the phone nice character. The number card is only reachable by undoing a bracket from the inside of the phone. Not easily accessable. A subscriber was certainly not supposed to do anything to this numbercard. Please not the 4 rest 51 7 kast klaardigit number. It was common in the Netherlands to only put the local number on. In small towns these telephone numbers could even be only 3 digits. I seems that for the original subscriber an extra digit was added as the local network grew. A one was added with pen, first on the outside of the window, later on the paper itself. Cleaned the window with a product called glassex. Yes it’s true. Name has been around for years. And in out language the last three letters have the same meaning as in English.

 

Broken cord, making a new one

rest 51 8 snoer 1So, here we are. All done. Everything cleaned, polished, reassembled. Only one minor problem: damaged handset cord. So I will make a new one.

What do we need?

1 mtr 30 cm of cord, made by by a company called Old Phone Works in Canada. It has red, blue and yellow wires as is standard for the cords in this era in Holland.

We need spades, piercing. Also made by OPW. The original spades were brass, nickel plated. Haven’t found a source yet for new ones. I do pry open old ones and reuse them, sometimes.

We also need piece of rubber, to protect the cord near the handset. I almost never see that on American phones, phones here are never without it. Tried al kinds of methods to find a good source for this part. Reused old ones, but they are usually to deteriorated. Now a use a piece of fuel hose for a moped. It fits exactly around the cord.

A piece of strong ribbon, to make a strain relief and black yarn. Original cords were wound with yarn at the ends to secure the strain relief, prevent the cloth covering unwinding and to secure the rubber bits. A rubber piece for the housing side of the cord wich acts as a strain relief. It is the same as the original rubber one. This one is made of vinyl and was salvaged from a PTT-phone from the 70’s. Exact same piece, but much more durable because it is made of vinyl. Good rubber ones are rare.

Superglue. I am not able to wind the yarn as tightly as they did back then. Furthermore the windings were coated with a kind of wax to prevent unwinding, in case of damage. I cannot make the cords as strong if I do not use superglue. The strain relief isn’t strong enough if I do not use it.

A tie-wrap. Same reason as superglue.

rest 51 7 snoer 2Make shure the black hose is cut straight. Doesn’t look good when it isn’t. Then slide back a bit of the cotton sleeve to expose the inner wires. Cut off one cm (oh darn, metric. Ehm 2/5th of an inch). Slide back the sleeve, so it is longer than the inner wires. You’ll need that bit longer to pull it through the hose. It takes a bit of twisting and turning, and you’ll need to grab that extra bit of sleeve to pull it through. Then slide it down the cord.

rest 51 7 snoer 3Measure out where the stain relief needs to go. Keep in mind the needed lenght of the yellow wire. In needs to go all the way through the handset. Then put the piece of ribbin lenghtwise along the cord and tie the yarn around it. The ribbon is going to be the strain relief. Now wind the yarn around the cord with the ribbon a dozen times or so, windings close together. Wind real tight!

Now fold back the end of the ribbon and wind the ribbon thightly rest 51 7 snoer 4around it. As tight as you can! Do the windings close together for about 1 inch in length. Cover the entire beginning of the ribbon, especially including the fold you just made. The ribbon is now anchored to the cord. It is really hard to pull loose now. This is how it was done originally. Mind that the rest 51 7 snoer 5cord with windings is not too thick to fit into the handset. Test fit the cord. Make sure the yellow wire is long enough and the strain relief is in the right place. Made the mistake of keeping it to short once. Had to do it all over again.

 

rest 51 9 snoer 9So, after making sure the yellow wire is long enough and the strain relief is in the right place, I can finish this end of the cord. I secure the yarn windings with superglue. I draw a line of superglue along the wound part of the cord, lenghtwise at three places. This prevents the whole thing from unwinding if the yarn is damaged and secures the strain relief. I’m afraid I cannot wind it as tight as they used to. They must have used a machine or a tool I do not have. Haven’t figured out how they did that. Also they used some kind of waxy substance after winding. I think it was to prevent unwinding after damage and to prevent fraying. Now I crimp the spades. I do not have a crimper yet, so I use pliers. This end of the cord is finished. I can fit it to the rest 51 9 snoer 10handset. The strain relief ribbon needs to be sandwiched between these 2 grooved little metal plates. Pull it tight, tighten the screw, slide the rubberrest 51 9 snoer 11 hose towards the handset untill tight. Presto, this bit is finished. See the picture on the right for the end result and an original one for comparison. IMHO looks pretty good and if done well, it is fairly durable. Suitable for daily use for years. I’m still puzzling over the way they used to wind these cords. The rubber bit was also wound, to keep it in place. Anyway, still to do the other end of the cord, then fit it and hang the phone up.

 

rest 51 9 snoer 12Now, the other end of the handset cord. The rubber thingy, that acts as a strain release is too narrow for the cord. As it is made of vinyl, that is luckily quite easy to correct. I  shove it over my yawl (priem in dutch) to stretch it to the right diameter. Then I heat the yawl with a lighter. I heat the strain release on the outside too, very carefully. I make the yawl really hot. Then leave to cool. I put it in my vise for that. Then slide it off. I might take a bit of effort. Now slide it over the cord to the correct lenght and a little beyond. Make shure you have enough lenght to connect it up. Wind with yarnrest 51 9 snoer 13 again, at the position where the strain release is. One layer of yarn is enough. Wind tighly again. Then do the same trick with the supergleu. Slide the strain release to the correct position. I use a tie-wrap to securde the strain release to the cord. Remove excess cloth covering, crimp on spades, connect all the wires.

I hung it up in our hallway. There I have a board put up to hang phones. I made it myself. rest 51 9 klaarSanded it smooth and sanded away the sharp edges, to give it an old fashioned feel. Then primed it white and gave it 3 coats of paint, again for that old faishoned look. Used 4 regular slotted screws (not Philips head!!!), brass, nickelplated, to mount it. I regularly change the phone there. My house is from 1934. A lot of woondwork, terrazzo floor, stainglass windows, panel doors. The phone really looks lovely there. Come and see!  Please note this was a basic restauration. The good conditionthis phone was in to begin with and its (not so) rarity make a deeper restauration unnecessary.

Hope you enjoyed reading this.

11 Comments

    • Dank je voor je reactie, Kees. Voor de vertaling heb ik Wikipedia aangehouden. Lighter fluid is hetzelfde als nafta en dat is weer een ander oplosmiddel. Mogelijk krijg je daar hetzelfde resultaat mee, maar dat heb ik nou eenmaal niet gebruikt.

  1. Hi, I have a very similar phone to this the microphone is not working, rings, dials fine.. So I was going to change it to a electronic mic, which one will I need? Thanks

    • Hi Kirsty, an electronic microphone will not work. It needs additional circuitry to make that work.
      The original carbon microphone modulates the current passing through it with the sounds it pics up. An electronic microphone generates a weak current with the sounds it picks up. The current it generates is too weak for telephone circuitry.
      I have a replacement microphone if you like, for 10 e excl shipping.
      Please send me an email on j_doubleyou@hotmail.com
      Regards,
      Arwin

      • I think Kirsty was refering to the electronic mics that do indeed have the built in driver circuitry to directly replace a carbon mic. For example the model 21A electronic mic that was a drop in replacement for the regular carbon mic in British 706 and 746 telephones. Link follows: The silver mic is the carbon version and the red one is the electronic replacement: https://antiquephones.blogspot.com/2012/07/21a-microphone-replacements.html
        Internally the active device is a standard small signal electret mic insert with an integrated circuit amplifier incorporating a relatively high current ‘Darlington’ output stage. The mic is also polarity insensitive just like its carbon counterpart.

  2. Thank you this post. I am a collector who thinking to begin to start in rotary telephone repairing and I find the most difficult part is how to remove the cover without breaking something. My next fear is I am afraid to damage something that is originally was working. Please advise.

    • Hi Sara, start easy and do not disassemble too much. Especially if the phone works fine. It can only get worse. 🙂
      Of course it is a different story when the phone is broken and needing repair.
      If you are not sure, ask around. Sometimes there is a trick.
      There are several forums on line, where you can ask your questions. And of course there are several groups on facebook, like mine: https://www.facebook.com/groups/vintageandantiquetelephones/
      You’re welcome to join.
      Regards,

      Arwin

  3. Thanks for the tutorial!
    I just purchased an older PTT rotary dial phone made in Holland and the line cord (green, blue, yellow and red) were connected to an old style 4 prong plug. I spliced it temporarily to a newer style 4 wire modular cord/plug. The phone did everything but ring when I called it, made and received calls and had a dial tone but wouldn’t ring. A friend told me a different way to wire it and it would ring but not make or receive calls. I have photos of the inside of the phone, the old plug with the 4 wires and the schematics for the two ways I wired it. Can you help me get this thing wired properly? Are you familiar with US phone wiring and color codes etc? Thank you

  4. Yes I have several pictures of the inside, I will email them to you but I found an older wiring diagram for these phones that Radio Shack here in the US supplied to the customers along with these PTT phones it sold to customers. I will email those to you also. Thanks

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