[Catkins]

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.