Turntable Cover Restoration
17/05/2022
Author: Karsten Hein
Category: Explorations
Tag(s): Restoration, Turntables
We might as well face it: Turntable covers have always been little more than a necessary evil. It seems that manufacturers—while suffering great pains in designing their beloved machines—were unable to think of anything more exciting than simply slapping a semi-translucent dustcover on top. And, typically, this cover was made of some easily scratched acrylic compound. For those of us searching for or selling vintage turntables these days, a scratched dustcover often meant a substantial degradation, not only in terms of attractiveness, but also in price.
Since the non-profit nature of my eiaudio testing series had made me rather price-conscious myself, I could not help but wonder just how much effort it would take to restore a scratched dustcover to its original splendour. The idea of being able to do so myself did seem attractive to the explorer in me. After all, this would enable me to take advantage of the potential price discount granted on the scratched cover, while being able to do the restoration myself. Hence, I contacted a friend, who also happened to be a specialist in automobile restoration, to help me find the best strategy for my project. Thomas was intrigued by the idea of restoring acrylic plastic and took the badly scratched dustcover of our Thorens TD 320, a turntable I had purchased some weeks earlier, to his repair shop.
Thomas returned the cover to me in mint condition just two days later and informed me which equipment I would need to purchase in order to complete this type of restoration by myself. I took note of his advice and placed my order on the same day.
Inventory Needed
- orbital sanding machine
- sanding paper, grades 240 - 3000 (240 / 320 / 400 / 600 / 800 / 1000 / 1500 / 2000 / 3000)
- orbital polishing machine
- polishing pastes in grades fine & extra fine (e.g. 3M ‘Green cap’ / 3M ‘Yellow cap’)
- one large microfibre cloth
The total tab would have set me back around 300.00 EUR, but, since we already had an orbital sander in the household, I only needed to purchase the various grades of paper and the polisher with the corresponding pastes and cloth. Thomas thankfully offered to keep me company during my first sanding attempt. On his advice, we took our little sanding project outside. This gave us cleaner air to breathe and protected our household furniture from the fine sanding dust.
The dustcover to be restored was of a 1978 Dual CS 721 turntable. Next to the typical house cleaning scratches, it also showed two lines of approximately 1mm in depth and 20cm length which had most likely come from piling other items on top of the unit during its years of storage. We discussed the most appropriate choice of sanding grain and decided to start from 320. If the scratches had been any deeper, we would have probably started from grain 240 to be on the safe side.
We positioned the turntable cover on an even non-slip surface and placed the sander firmly on top of it. The speed dial was set to medium revolutions in order to keep the temperature low during the process. If the temperature became too high, the cover could easily become stained or deformed. The sander was placed on the surface with the motor turned off, and it was turned on only when securely in place. This way, there was less chance of the paper’s sharp edges accidentally cutting new scratches into the surface.
Thomas explained to me that the machine would need to evenly sand the whole surface until reaching a ‘level 320 sanding result’. (Note: Be sure to keep your fingers away from the paper edge, as this can indeed be quite sharp and easily cut into flesh.) Starting from grain level 320, the turntable cover did become opaque at an instance, and we knew that it would take some time for it to become translucent again. On the positive side, we could watch the deep scratches gradually disappear. We had peeled the Dual logo off with a screwdriver before sanding, and we made a point not to polish the edges of the small cavity where the logo had originally been placed.
Thomas insisted that we take the time to fully complete each step of the sanding process, thus working our way up from 320, to 400, and then to 600, until all the steps to 3000 had been completed. At each level, we made sure that the surface was fully restored to the level characteristic of that grain. We stayed out of the sun and took breaks to keep the material temperature low. At grain level 3000, the surface started to become translucent once again. We inspected the final result by wiping the surface with the large microfibre cloth.
Once we were happy with the sanding result, we exchanged our sander with the polisher. Thomas explained that it was best only to use small amounts of polishing paste, as this would otherwise splash about in a circle. As we had done during sanding, we turned the machine on and off while it was in contact with the turntable cover. Thomas showed me how to apply even pressure in order to achieve a uniform result over the whole surface. I saw that one small scratch we had missed in the early stages of sanding also managed to survive all the stages of further treatment. To me, this only highlighted the importance of a very thorough first sanding.
We checked the polishing result from time to time, until no further progress could be made using the '3M Green' cap paste. It was only then that we changed to the '3M Yellow' cap paste for that final high-gloss polish. Pleased with the result of our work, we found ourselves ready to tidy up the scene of the action approximately one hour after we had started. One hour’s work is probably a good estimate for anyone doing this the second or third time around. I was lucky that I had the help of my professional friend who had made sure I took the correct time and followed all the steps necessary. First time polishers would probably be best off to calculate with 2-3 hours of manual labour.
I hope you will find this account of events helpful in your own restoration project, even if it is only to help you better appreciate the prices charged by professional restorers. Do feel free to leave a personal comment below. With 'Hyvor Talk', we have recently made social engagement on this platform far easier. — Enjoy.
