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UK GPO 746 Topaz Yellow Telephone Restoration

Started by royalbox, January 16, 2017, 09:01:58 AM

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andy1702

Sounds like you're working along the right lines there Barry. I've not tried the plastic disolved in acetone crack repair yet, but I think it will work judging by the results on other threads.

I do have a green cased 706 here somewhere that I seem to remember had a nastyu crack up the side of the case all theway to the dial hole. I originally repaired it by putting superglue on the back of the crack and letting it run in by capillary action. But like you said, it still looks like a crack. So I might try digging the phone out from wherever I put it, V-ing out the crack and having a go at the same thing you're trying.

What I'd really like to know is does this disolved plastic trick also work on diakon? I have an black diakon case that got damaged in the post and I'd previously thought may be beyond salvation. But if it can be welded in this way it could be the answer.

As for the crazing on your vapour treated phone... I wonder if it's something to do with vapour collecting on the lid, condensing and dripping back onto the case? What would happen if you fitted a small electric fan (maybe from an old computer) in the box to circulate the vapours? Just a thought.

Andy.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

royalbox

Hello Andy,
So far I've dabbed on liquid at least 10 times but there is still a groove. I read this post where he ended up just dabbing acetone on some ABS to soften it then scraped it off and pasted it into the groove. I'd recommend waiting to see how mine turns out before trying it on your green phone, I'll keep you informed of how it goes.

You could be right about the vapour condensing and dripping, as there were a few marks here and there that looked liked something had dripped.
Good idea about the fan. One of the youtube videos on vapour smoothing used a PC fan but it must be one that doesn't dissolve in acetone obviously, but also must be brushless (if I remember correctly) so as not to cause a possible spark. Think I'll look that video up again to check and get a cheap fan. Definitely worth trying.

Barry.

royalbox

Also, I bought a couple of original false buttons in grey and blue that were on ebay. They could be a good source of ABS to disolve for filling cracks and mending breaks as they may be closer in colour and material than the newly manufactured ones.
Barry.

royalbox

Just a couple of pictures of progress on the grey phone:

1. The groove cut along the crack.
2. Groove filled with dissolved plastic from the supporting ribs inside the phone.

I dabbed the liquid into the groove. Once the acetone evaporates, it appears to me that some of the plastic creates a hump either side of the groove if you see what I mean. I'm not entirely sure whether the groove is filled or whether it is still below the surface of the rest of the case. Won't know until it's sanded I suppose. Hope I can get it looking good with sanding. Will leave it for several days or a week to harden.
Barry.

andy1702

I wonder if you've made your liquified ABS a bit weak? I saw something written somewhere that said you should only use a little acetone but disolve plenty of ABS into it so it makes it more of a runny paste rather than a liquid, then smooth it on with some kind of tiny spatula.

Andy.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

royalbox

Hello Andy,
I used 4 small sliced-off pieces of plastic from the inside supports and a tiny bit of acetone. After I'd finished applying the liquid as above I decided to let the acetone evaporate a bit to see if I could get a paste like consistency. However, being such a tiny amount, it went from runny to completely evaporated in a very short time. I think you'd have to dissolve quite a bit of plastic to be able to get a thicker consistency.

I sanded the repair and sure enough as was mentioned in that other post I linked to earlier, air bubbles appeared. Also, the repaired section is a bit darker than the surrounding plastic. Not a great success. It's currently drying, but I'll see what it looks like after the next "vapour trial" once the cheap fan I ordered has arrived.
Barry.

andy1702

Reading through that other thread, it appears the air bubbles come from the solvent as it evaporates from within the disolved plastic patch. So I'm now wondering if there is a different way of liquifying the plastic without using solvent.

I know some 3d printers and also some of those 3d pens use ABS, which is heated up in the unit and spat out the nozzle as a stream. This has made me wonder if you could use a thin rod of ABS and an electric soldering iron to melt the crack and apply more material at the same time? As this doesn't involve solvent there shouldn't be any way for the air bubbles to form. I'll give it a try on a bit of scrap ABS and let you know what happens.
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.

royalbox

Thanks Andy, I will be interested to see how you get on. I've also got a green one with a crack in a similar place and a blue one with a piece missing from the front edge.
Barry.

twocvbloke

Quote from: andy1702 on February 04, 2017, 12:44:51 PMI know some 3d printers and also some of those 3d pens use ABS, which is heated up in the unit and spat out the nozzle as a stream. This has made me wonder if you could use a thin rod of ABS and an electric soldering iron to melt the crack and apply more material at the same time?

You'd probably want to have a soldering iron with a variable temperature, too hot and you'll burn the plastic, which not only ruins the look, but also smells really bad...  :o

WEBellSystemChristian

Wow, this is the first time I've read this topic!

I'll address the most recent issue first. I've found that bubbles formed in Acetone 'pools' are very easily repairable. Simply put a drop of pure Acetone on the patch of bubbles, and 'blot' it out with your fingertip until the bubbles disappear, then let dry and sand.

I'm glad to see the chemical polishing method works for someone else! What is your phone made of? ABS? Tenite?

If it's Tenite, straight Denatured Alcohol (or mineral spirits) and polish (Novus #2) will work great. That will get rid of the surface imperfections your phone has after polishing.
Christian Petterson

"Whether you think you can or think you can't, you're right" -Henry Ford

twocvbloke

Quote from: WEBellSystemChristian on February 06, 2017, 10:03:34 PMWhat is your phone made of? ABS? Tenite?

Pretty much all GPO phone shells after 1962 are made of ABS, prior to that it was Diakon (polymethyl methacrylate, also known as Perspex), we never used Tenite here for our phones, just Bakelite, Diakon and ABS...

royalbox

#41
Sorry it's been a while since updating, experiments have been ongoing though. I've had a few disappointments but yesterday had some great success.

First, thanks for the tip Christian. The other problem is that the patch is darker than the surrounding plastic. I need to sand the grey phone again now so have moved on to the original yellow phone of this thread.

I've been doing the ear and mouth pieces using the setup in the first picture. I'm using an empty Vanish "oxy-action" carton. Around the inside edge at the base is a piece of kitchen paper folded twice and held in place by magnets on the inside and outside of the carton. A piece of cardboard tube taped to the lid holds the ear/mouth piece in place. I clean the pieces with methylated spirits (denatured alcohol) and put blu-tack around the threads so they don't get exposed. Some acetone is dribbled onto the paper towel and the carton is screwed onto the lid (upside down). I leave it for 15 minutes and carefully unscrew the carton and remove it. I'm really pleased with the results, very smooth and shiny with no noticeable scratch marks.

Next post will be the yellow phone case.

Barry.

royalbox

#42
I decided to have a go at the yellow phone case. As the ear/mouth pieces worked well with the acetone soaked paper above them, I decided to do the same with the case. I used 2 sheets of kitchen paper taped to the lid of the case and other pieces around the edge. I also raised the phone up nearer to the top of the box than I had been with the grey case. No fan, just soaked the towel on the lid and added some around the sides. Put the lid on and waited 15 minutes, took the lid off and couldn't believe how good it looked. Nice and even treatment, very smooth and shiny.

There are a couple of places where I could have sanded more to get rid of the discolouring but it's hardly noticeable. Strangely, the ring under where the dial surround goes came out slightly less shiny but it doesn't matter as it's covered by the surround of course.

It came out so well that I decided to re-sand the handset before "vaping" to get rid of the still slightly discoloured areas. I'm very fussy.

Barry.

TelePlay

Quote from: royalbox on February 11, 2017, 10:12:22 AM
The other problem is that the patch is darker than the surrounding plastic.

That would make sense in that the interior plastic would not be changed by exposure to exterior conditions, inside is the original color while the housing exterior is probably faded, in this case. If the housing were darkened over time, the patch would be lighter.

That is a very nice looking yellow housing.

andy1702

I'm very impressed by those results! Looks like this could be the way to go to get a nice shine back on ABS, which never seems to be as shiny as Diakon.

Now I'm looking for a way to restore discolouring, particularly on grey and ivory cases, that doesn't involve having to expose them to sunlight, because here in the UK we don't have any !

Andy
Call me on C*net 0246 81 290 from the UK
or (+44) 246 81 290 from the rest of the world.

For telephone videos search Andys Shed on Youtube.