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Old 7th Jan 2019, 8:34 am   #61
Catkins
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Default Re: 1938 Murphy A56V television restoration

Apologies for the lack of follow-up posts. First that is because the long Christmas holiday is perfect to do some in-depth restoration and I have been busy doing my next television restoration. Second on a more personal level, there was a death and a stroke in the family over Christmas, and that obviously took priority.

Once I'd stripped off most of the components that needed work on them, the next stage unsurprisingly was to slowly restore them. In conjuction with rewiring and repainting the chassis (which could be done in parallel), this took about 1 and a half years.

With so much to choose from, the first thing I did was to restuff all the waxy capacitors, and in parallel derust, and restore the CRT clamp/focus coil adjustment mechanisms Why do this first? Because this was easier "low-hanging fruit". After about 4 months of ever-more dispiriting stripping down, it was better to start with things where I could make rapid and solid progress, and especially stuff which I could do in the evening after work. Additionally, it also gave me time to research and think about how I was going to approach some of the more difficult parts of the restoration, including time searching for NOS components.

Moving onto waxy capacitor restuffing. This is a necessary if fairly boring task. In my experience no waxy capacitor from the 30s has survived in full working order due to their nature, and are at best leaky and vastly over-capacitance, and are often open-circuit or short-circuited. You may get away with not replacing those waxy capacitors in a 30s radio, but they'll cause numerous problems in a 30s television. I tend to prefer to eliminate those problems from the start by restuffing them before trying to get the set working, and then concentrating on the real faults when you first turn on the television.

Obviously lots of people have their own techniques for waxy capacitor replacement. Some just replace with modern components, some make the modern components less visible by covering them with black sleeving. It all really depends on how important you think preserving the original look is.

Personally in a rare 1930s television I think is it worth going the extra mile, and preserving the exact look. Doing this makes the restoration more difficult, but perhaps more authentic.

This means restuffing the original waxy capacitors. Even there it seems there's many different approaches. In my first restoration of a HMV 904, I slit the waxy capacitors length-ways, removed the contents, replaced with a modern component, and then glued the waxy capacitor back together with hot glue. As long as the slit can be hidden in a non-visible place this works well, the original look is preserved exactly.

For this restoration I tried a different approach. I noticed the capacitors used in the Murphy were significantly more waxy than the waxy capacitors used in the HMV 904, including a layer of wax inside the paper envelope. This led to the idea if could I heat the wax up using a heat-gun, could I then slide the contents of the capacitor out without any slitting of the paper envelope? In fact I discovered I could do just that. But, of course, it removes all the wax from the capacitor paper envelope.

So the process became heat-up the capacitor removing all the exterior wax. Then heat up the paper-envelope allowing the crimp on one end of the capacitor to be folded back, and the contents slid out.

The new modern capacitor(s) is/are then soldered to the original two metal end-points, then the contents put back in the paper envelope. The envelope is then heated to allow the crimp to be re-crimped. Lastly, it is then redipped in hot new beeswax.

This leaves a waxy capacitor which is indistinguishable from how it looked originally.

Photo 1 shows ten waxy capacitors removed from the set. Photo 2 shows an example of the replacement of the original contents with two modern capacitors. Photo 3 shows the 10 restuffed and redipped capacitors.

Initially when it came to heating up the new beeswax for redipping, I hit a number of problems. If the beeswax gets too hot then it has a nasty tendency of self-igniting which isn't very fire safe. But if the wax isn't kept hot then the dipping is poor, the resultant wax coating is too thick and not evenly distributed. I needed to discover a way of keeping it hot enough for a good result, but not become too hot that it caught fire.

Serendipitously I had recently bought a glass teapot and teapot warmer (to keep the tea hot). I discovered if I put three teelights in the warmer then it provided enough heat to keep the beeswax at the right temperature, and not get too hot.

Photo 4 is a photo of the hot beeswax on top of the warmer. The beeswax is in an old tuna tin
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Old 7th Jan 2019, 10:21 am   #62
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Default Re: 1938 Murphy A56V television restoration

Beautiful and well worth doing.

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Old 8th Jan 2019, 3:53 am   #63
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Default Re: 1938 Murphy A56V television restoration

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This means restuffing the original waxy capacitors. Even there it seems there's many different approaches. In my first restoration of a HMV 904, I slit the waxy capacitors length-ways, removed the contents, replaced with a modern component, and then glued the waxy capacitor back together with hot glue. As long as the slit can be hidden in a non-visible place this works well, the original look is preserved exactly.

For this restoration I tried a different approach. I noticed the capacitors used in the Murphy were significantly more waxy than the waxy capacitors used in the HMV 904, including a layer of wax inside the paper envelope. This led to the idea if could I heat the wax up using a heat-gun, could I then slide the contents of the capacitor out without any slitting of the paper envelope? In fact I discovered I could do just that. But, of course, it removes all the wax from the capacitor paper envelope.
Phillip did discover this alternative approach by copying me One of these days I'll get round to doing a proper write-up of my HMV 907 restoration where I used it. The use of the teapot warmer is, however, entirely down to Phillip

I used an old tuna tin which I heated up on the stove. It took a lot of experience to judge exactly when to take the tin off (wax at the right temperature to get a coating of the right thickness). You then had a short time to get the capacitor done before the wax was too cold. One time I put the tin back on and forgot about it and it caught fire (tall flames and lots of smoke)...

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Old 8th Jan 2019, 4:29 am   #64
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Default Re: 1938 Murphy A56V television restoration

Quote:
One time I put the tin back on and forgot about it and it caught fire (tall flames and lots of smoke)...
Not really forgot - more like left it on too long while examining my latest capacitor. The fire was quickly put out using the fire blanket next to the hob, but a safer approach was obviously needed...
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Old 9th Jan 2019, 3:09 pm   #65
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Default Re: 1938 Murphy A56V television restoration

Hi Catkins,
I've loved reading your write up of the A56V restoration.
The hot wax capacitor dip is a nice idea. I wonder if the heaters used for hair removal wax would work?

Cheers
Andy
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Old 10th Jan 2019, 9:24 am   #66
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Default Re: 1938 Murphy A56V television restoration

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I wonder if the heaters used for hair removal wax would work?
I use an old slow cooker, works a treat!

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Old 14th Jan 2019, 6:39 am   #67
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Default Re: 1938 Murphy A56V television restoration

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I've loved reading your write up of the A56V restoration.
The hot wax capacitor dip is a nice idea. I wonder if the heaters used for hair removal wax would work?
Strangely enough I saw some in Lidl's over Christmas, until then I was unaware any such products existed I suppose the key as to whether they'd work is whether "hair removal wax" liquefies at the same temperature as beeswax. I guessed that hair removal wax would melt at a low temperature to avoid burns - beeswax gets quite hot at the "right" temperature for a successful dipping. I wouldn't want to have an accident and tip the hot beeswax over my hand .

Regards

Phillip

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Old 14th Jan 2019, 7:40 am   #68
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Default Re: 1938 Murphy A56V television restoration

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I use an old slow cooker, works a treat!
That's a good idea But I suppose it really depends on your slow cooker.

Earlier in the thread I mentioned I hit on the idea of using a slow cooker to bake the transformers (EHT and Mains) prior to reassembly.

But, I tested the temperature to ensure it never got hot enough to melt the wax in the transformers, as that's obviously that's something I didn't want to happen. I found the slow cooker over about 8 hours never got hot enough to do that (the temperature regulation isn't perfect, and it gets a bit too hot after about 8 hours).

Due to that finding it didn't occur to me to use a slow cooker.

But, it is obvious from your statement that different slow cookers have different temperatures!

Like everything, this is really a question of trial and error, finding something close at hand that works.

Tealights and slow-cookers so far. Anyway found a third solution?

Regards

Phillip
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Old 14th Jan 2019, 8:09 am   #69
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Default Re: 1938 Murphy A56V television restoration

I’ve used an old 500 Watt halogen lamp controlled by a dimmer to melt the wax on capacitors before.

The lamp is positioned above a tin to catch the wax. The old innards can then be pulled out leaving the card sleeve intact, ready for re stuffing.

It works well, but does need some experimentation to get it right!


SimonT.
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Old 15th Jan 2019, 7:19 am   #70
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Default Re: 1938 Murphy A56V television restoration

On with the story. The previous post mentioned the capacitor restuffing, and the CRT clamp/focus coil adjustment mechanisms restoration. Photo 1 shows the dismantled and derusted and cleaned-up CRT clamp/focus coil mechanisms. From the photo it should be obvious this consists of quite a few components, and it obviously got vastly simplified in later sets.

I decided to do this work first, as it allowed me to look for NOS components and generally do research on the other aspects of the restoration in parallel. As hoped, this worked well, and by this time I had found good contemporary replacement parts for the various missing mica capacitors, the open-circuit trimmers, and the wiring.

So now I could get on with the other aspects of the restoration. But the thing I next choose to do was to tackle the badly rusted and corroded metal-work on the main chassis. Out of everything this was the thing I was most concerned with, as I still didn't entirely know how to tackle it. I had done some research in parallel with the capacitor restuffing about dealing with badly corroded metal-work, but it was inconclusive. It didn't give any easy answers, but it left possibilities that I wanted to try out.

The problem was the metal-work on the chassis was badly rusted and corroded, but, unlike the metal-work on the transformers, it was relatively delicate and thin at the beginning. So rust and corrosion had penetrated to perhaps 40-50% of the original thickness. There is not a lot you can do with that, hence my problem.

Photo 2 is a photograph of the audio output transformer. It should be clear that it is heavily rusted, but, it is also pock marked with much deeper penetrated corrosion which shows up as black areas.

Treatment with a chemical rust remover produces Photo 3. It is much thinner than previously (minus the thick layers of penetrated rust), it is deeply pitted and covered with impurities due to corrosion that the rust remover hasn't removed. What is not shown is the metal surface is very soft.

What can I do with such a metal surface? The pitting and general poor quality surface is certainly not very attractive.

The normal solution to this is to grind out the impurities and the pitting, and so to get back to a flat surface consisting of the good metal underneath.

My problem was I couldn't do this (even if I wanted to, which I didn't), because the metal-work was already thin and fragile. Any process of grinding back to good metal would quite likely result in it falling apart on reassembly.

My only choice was to try and build it up in layers. The first idea I had was to paint it in multiple layers, sanding down between layers to finally produce a reasonable flat surface. I was not convinced this would work, but, I gave it a try. Photo 4 is the result, which I considered to be a complete failure.

The surface was not only not very flat, but, it was also quite obviously painted with silver paint. I'm not a great fan of repainting previously plated metal-work with silver paint, as it aways looks to my eyes a bit naff.

As I decided the silver paint was completely unconvincing, it also eliminated my second approach (before I even tried it), of covering the metal-work with something like chemical metal, sanding that down to a flat surface, and then painting it.

Something more sophisticated was clearly needed. In my previous researches I had considered replating. But I had discounted that due to the heavy pitting in the metal-work. Plating doesn't work well with deeply pitted metal, as it makes the pitting even more visible. If you plate you must start with a good surface to begin with (otherwise garbage in garbage out). The way to do that is to grind back to a flat surface. But then we're now back to square one.

But I had read in passing that there was a rarely used way of plating that produced a good surface without grinding. It was rarely used because it was labour intensive and expensive. But, perhaps, that was worth a try.

It did work, but it was very labour intensive. Photo 5 is the resultant replated metal-work.

But, the process involved with have to be for the next post.
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Old 31st Jan 2019, 2:31 pm   #71
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Default Re: 1938 Murphy A56V television restoration

Apologies for the delays in posting, January is a busy month in work, as I have to travel to Brno, Czech republic for conferences and meetings (posting from Brno airport now).

Anyway, the last post mentioned there is a way of plating without grinding down to good non-pockmarked metal. That is perhaps obviously by building it up to a good surface by repeated plating and polishing. Obviously this is difficult to do especially with hard metal like zinc and nickel. So the way of making this work is to plate with copper, which is soft.

But you can't plate with copper directly over steel, as it will react. So first you must plate with a 'flash' layer of nickel, which doesn't react with either steel or copper. Then you can plate with copper, polish it down, and repeat. The more you repeat this, the better the finish becomes.

All in all I made about 5 to 6 plates of copper, which gave a good mirror finish. Photos 1 - 3 shows some of the progress, the finish getting better. The first photo shows some plating "burns", this is normally unwelcome because it gives a poor finish but here it is an artefact of doing a longer plate than normal, to produce thick plating. As the plating will be polished down it doesn't matter.

Once the copper plating has been finished, you can put a final plate of nickel on top, which looks OK. But I personally found zinc produced a less chrome looking finish than nickel. As zinc will react with copper (to produce brass), you have to first plate with nickel anyway, and then add a final layer of zinc.

In photo 4, the left bracket has been nickel plated, the right has had an additional plate of zinc. The bluish tinge is due to passivation.

Photo 5 shows a collection of replated metal components.
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Old 31st Jan 2019, 8:20 pm   #72
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Default Re: 1938 Murphy A56V television restoration

Hi Catkins, was this a home plating plant or industrial?

If home, how easy was it to source the chemicals and what sort of power supply did you use?

Ed
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Old 31st Jan 2019, 8:43 pm   #73
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Default Re: 1938 Murphy A56V television restoration

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Hi Catkins, was this a home plating plant or industrial?

If home, how easy was it to source the chemicals and what sort of power supply did you use?

Ed
We bought 3 home plating kits from Classic Plating (https://www.classic-plating.co.uk/). A bright nickel plating kit, a copper plating kit and a zinc plating kit. The kits come with a Variable Current Controller (just a bit of resistance wire) which you connect up to a 12v supply (e.g. car battery). However, it's very hard to control the plating current using this, so we used a bench power supply.

The first kit we got was the nickel kit which I used to plate the screening cans on my HMV 907. We were initially unsure about how successful the home kits would be, but based on this we got the extra kits to extend the finishes we could do. For general plating, zinc looks closer to the original finish than nickel (but the screening cans appear to have initially been nickel plated).

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Old 8th Feb 2019, 5:48 am   #74
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If home, how easy was it to source the chemicals and what sort of power supply did you use?
Hi,

As my brother said, they were home plating kits, supplied with all the necessary chemicals and plating anodes (copper/nickel/zinc). Each came packed into a white plastic bucket, which later becomes the electroplating tank. Photo 1 shows the copper plating kit in use.

You do have to add a couple of extra things (obviously depending on whether you already have them). In addition to the electrolyte solution, you also make up a degreasing solution, an acid "pickle" solution and a passivate solution (the third only for zinc electroplating), and you need to provide tanks to put them in, preferably sealable for later storage. The solutions will attack some plastics, and so you need to ensure any plastic tanks are of a type that won't be attacked. We found sealable plastic tubs designed for storing food left-overs in the fridge to work very well here.

The chemicals are supplied in plastic bags, and are not the exact amount you need to make up the initial solutions (this is presumably so you can top up the electrolyte and make more degreasing/pickle solutions once they are exhausted, from memory there were enough to make up at least another fresh solution). So you need to have a set of scales which can accurately measure fairly small quantities, to correctly make up the electrolyte and other solutions.

An important addition, as mentioned by my bother, was a bench power-supply. Using this you can accurately control the amount of current being used. The reason for this should become clear later.

But obviously the most important "addition" was time. Websites state you can get good results with home plating kits, but it takes a lot of practise. Something which we found to be very true.

I obviously first started experimenting with odd bits of metal which could be thrown away afterwards. This was to get experience with the process and to get a feel for all the variables at play, there are lot of variables and it is those which make the difference between a good plate and a terrible plate.

Before plating you have to prepare the metal, to make sure it is clean and free from contaminants. First you put it into a degreaser, this is obviously enough to remove grease and other dirt. A couple of minutes is recommended depending on the temperature of the degreasing solution (the hotter it is the more quickly it works), it is better to overdo it than underdo it, but with any powerful alkaline/acid solution there is also too long, which will damage the surface. Next you put it into an acid "pickle" solution, which removes contaminants, this is for about 30 seconds for steel. This is strong acid and will literally eat away at the metal if left in too long. If you're adding an additional plate, it is an easy way to remove your previous plate(s) at this time, as experience tells.

The above times are guidelines and with practise you start to get a feeling for when and why you need to vary them to get a better result.

Next you put it into the electroplating tank and turn on the power. The electroplating solution will take all the current you can give it, at whatever voltage you select. The question is what is the best voltage and current to get the best plate? The guidelines provide a start, which is xxx voltage (this differs between copper/nickel/zinc plating), and so much current per square inch of metal surface (the larger the surface the more current is drawn).

The surface area to be plated, the voltage and the current all ultimately determine the rate (or speed) of plating. The more surface area the slower the plating for a given voltage/current. The higher the current/voltage the faster the plating, irrespective of surface area, but obviously you need to increase this as the surface area increases to get the same rate of plating. There is a sweet spot between too slow plating and too fast plating. Too slow plating results in coarse and dense plating which is not attractive. Too fast plating results in fragile plating, it can often be easily flaked away as it doesn't stick. Even with the right current you can also get plating burns which is uneven plating due to current eddies in the electrolyte (uneven distribution of current). This is often due to poor placement of the component with respect to the anodes, to get perfect even plating all parts of the component need to be the same distance from an anode.

To add to this you have the additional variables of plating time, and electrolyte temperature all of which affect the resultant quality of the plate.

With so many variables at play it is not surprising that the vast number of home platers get poor results. Doing a lot of reading (for pitfalls) and a fair amount of practising, I got better and better, you slowly get a feel for what is right. That is not to say I didn't experience some major disasters, I had plenty of them along the way, but I learnt from my mistakes and started again and again, until I got it right.

While looking for photo 1, I discovered photo 2. Photo 2 shows two metal "backs" from potentiometers that were mounted on the front of the case (providing the contrast, brightness and focus controls - the volume control is different as it also has a double pole switch). The left back is completely untouched, and it can be seen to be extremely rusted and corroded. The right back was orginally similar in appearance, but, it was treated, prepared for electroplating, and then given one plate of zinc electroplating at a carefully controlled current. For one plate, the results are very good, and it looks almost new.
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Old 8th Feb 2019, 10:00 am   #75
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I used an old tuna tin which I heated up on the stove. It took a lot of experience to judge exactly when to take the tin off (wax at the right temperature to get a coating of the right thickness). You then had a short time to get the capacitor done before the wax was too cold. One time I put the tin back on and forgot about it and it caught fire (tall flames and lots of smoke)...
I started re-stuffing wax paper capacitors back in the 1970's. Also re-painting resistors with body-tip-spot color coding and re-wiring sets with fabric wire. I got a lot of very odd looks from other technicians back then.

Over the years I found the ideal method for wax-paper caps was to heat them in an oven until the wax just melted. Then pull and or push the innards out. The trick then is to wipe the paper tubes down with a paper towel, that absorbs the dirty melted wax.

On fitting the new caps inside, fibreglass tape is used to build up their diameter, to a push fit in the sleeve. Then, on alternate days, polyester resin (the type that uses a catylast) is poured into each end. This has an opaque look to it, somewhat like wax, but won't melt or attract dust (Photo of some from a TV restoration attached).
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Old 8th Feb 2019, 10:50 am   #76
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To add to this you have the additional variables of plating time, and electrolyte temperature all of which affect the resultant quality of the plate.

With so many variables at play it is not surprising that the vast number of home platers get poor results.
You are right about this and its not just home platers either. It took me a while to find commercial electroplaters that I could trust with delicate components from vintage radios & TV's.

I really admire what you have done with your restoration, because you are not prepared to settle for average and you put in the extra work to figure out how to electroplate items yourself.

Also, that you understand the importance of eliminating rust and corrosion.This is not just for the cosmetic appearance, which is vastly improved, but it is also the only way to have a long lasting restoration. More to the point, to preserve a piece of electronics history for future generations.

Many restorers underestimate the long term destructive effects of rust and corrosion and do not realize that it has to be stopped in its tracks, for any project that can be called a real restoration.
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Old 16th Feb 2019, 2:42 am   #77
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Default Re: 1938 Murphy A56V television restoration

I spent quite a while replating all the various pieces of metal that needed restoring. Picture 1 is an additional photo of one of the replated brackets on the deflection coils, and shows quite a good mirror surface has been obtained. I have lots more pictures of the replated parts, but, I think it is important to get on with the story.

After doing the plating, I took stock of what I needed to do next. The obvious one was to reassemble the various components that had their metal bits replated. This meant the transformers, the scan coils, the potentiometers, putting the potentiometers back onto their replated mounting brackets etc.

While reassembling the potentiometers, I took the time to test them, and fix any of the potentiometers that didn't work. Some were just dirty, and needed a good clean. Some were discovered to be open-circuit on the resistance track. I used the same trick to fix them, as I did previously with the HMV 904 potentiometers. I used layers of conductive silver paint to join the breaks on the track, which also had the side effect of bringing the over-all resistance back to within tolerance.

Photo 2 shows one of the potentiometers repaired with silver paint. Photo 3 shows the repaired potentiometers replaced on the replated mounting brackets.
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Old 16th Feb 2019, 3:52 am   #78
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Default Re: 1938 Murphy A56V television restoration

Continuing with the progress in chronological order, and a time/progress check. By now it was around November 2016, and I had spent a year on the restoration so far. I also had a two week Christmas vacation from work looming up. This was important, because my vacations are very good times to get time consuming difficult and/or fiddly stuff done which requires concentration and lots of time not doing anything else.

So it was an obvious step to look at what I had to do next and plan accordingly. I had the treating and respraying of the main chassis to do, the complete rewiring of the chassis, and then the slow process of initial reassembly, putting back the waxies/electrolytics, the transformers etc.

Both the rewiring and initial reassembly would be better done on the vacation when I had the necessary concentration. The respraying would be nice to do then too, but I can't respray and rewire at the same time. This meant I had to do at least some of the respraying before the vacation to let it harden, or leave it until after Christmas entirely.

So the next stage was to finish off stripping the components from the surface of the main chassis, and start some initial resprays. But, as each layer takes a week to harden, I also had time to do other things, but obviously not rewiring or reassembly which I was waiting until Christmas to do.

What I did in the meantime was to restore the loudspeaker. Photos 1 & 2 show the original condition of the speaker. It is one of Murphy's huge mains energised loudspeakers with a large cast iron case containing the field electromagnet. Like everything else it was rusted and the wiring needed replacing, but thankfully there was nothing else wrong with it, and the coils and cone were intact. It obviously came up well with rust treatment and a couple of layers of new paint. Photos 3 & 4 shows the not too unsurprising result.

After that, I spent some time cleaning and polishing the removed AF/IF coil cans, and putting in new rubber grommets. This is work which is ideal for the winter evenings after work, as it takes time but doesn't require much concentration and can even be done while watching a DVD.

Photo 5 shows the again not unsurprising result.
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Old 16th Feb 2019, 4:33 am   #79
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Default Re: 1938 Murphy A56V television restoration

One trick I discovered for restoring very old speakers, often the paper has dried out and become quite brittle. If that has happened it is possible to rejuvenate it by using a solution of 3 or 4 parts of mineral turpentine to 1 part of Linseed oil. It is gently brushed on with a very soft brush (like a makeup brush). After a day the turps evaporates leaving the small amount of linseed oil in evenly dispersed in the paper.
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Old 16th Feb 2019, 5:09 am   #80
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Default Re: 1938 Murphy A56V television restoration

That is a very good trick, which I'll try and remember for next time Luckily, the cone on this speaker was still flexible and showed no signs of brittleness.

But I have bought sets with brittle cones, and often times you only know that *after* you've bought it and had it shipped via a courier, only to discover the cone has shattered into many small pieces. At that point there is nothing you can do about it, except be wary next time.

The first time it happened to me was way back in 1997, when I bought a 1930s Philips super-inductance set from Steve Harris (On the Air), and had it shipped via courier. As I said the cone came back in pieces and totally ruined. But since then I have had generally good results with 1930's sets. This one may have been just bad luck.

But, I have found 1920's moving iron speakers to be more brittle, and if you get them sent via courier they invariably arrive with the cone torn away from the movement or worse. It is always better to pick them up in person, or avoid this and buy from an auction or NVCF.

1920's speaker cones in general are as brittle as bakelite and both you should never get sent via courier, otherwise you're simply throwing your money away.
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