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Holmes’ Files: Thorens Project, Part 1

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In the beginning, there were two choices: Thorens TD124 and Garrard 301. I had a Garrard 301 grease bearing white-paint version, and a TD124, MkII non-magnetic platter, so I won’t blow up my moving-coil cartridge. Both were in original plinths, looked like they had been in an attic for 20 years (because they had), and neither worked. So, already having a nice direct-drive, i.e. the Denon DP80, and a tweaky oddball, my Versa Dynamics 1.0, I decided that I would keep only one. After closely examining both units, my opinion was that the TD124 had a quieter motor, and better build quality. I then traded the 301 to John, the plinth builder, at Porterhouse Audio for a custom plinth built for my TD124. A very special plinth it is. John uses multiple layers of Panzerholz of a type built for underwater applications, and not an “off the shelf” product. It has more resin, and is more highly compressed than production Panzerholz. I’ve never seen any product like it. It’s literally bulletproof: Panzerholz was originally designed to be an anti-ballistic material. It has machining characteristics that are closer to plastic. Since it is built up of highly compressed alternating layers of wood, it is critically damped. All that, and it looks damn cool. There are two layers of Panzerholz with a layer of Basswood between. It is a hard-soft-hard combination that usually works well for plinth building.

One of the reasons I wanted a TD124 is the super fast armboard swapping you can do. If you, like me, have some different tonearms lying around, all you have to do is buy an additional armboard, mount the arm, and leave it permanently mounted on the board. Just swap armboards and you’re done. In addition to making the plinth big enough to accept a stock 12” armboard mounted directly to the Thorens, I wanted the capability of having a second arm permanently mounted on the backside of the table. What John created was more elaborate and better conceived than anything my feeble mind would have dreamt up.

Everything was moving along until John discovered my TD124 chassis was warped. Warped? Apparently someone dropped the unit at some point in the past, I guess. I couldn’t find any dings or cracks, but it was warped somehow. Luckily, some time before this I had purchased a stripped TD124 chassis on eBay with the idea of experimenting with finishes. The chassis was the worst example I’ve seen, with scratches, dings and chipped paint. I’m at a loss to understand how it got to that point. I’m just lucky that I got it for $50.

The next decision was what finish would I choose when fixing the trashed out chassis? Paint seemed a logical choice, but I wanted to take this project somewhere different. The chassis, made of an aluminum alloy, presented several different finishing options. Since I work in a machine shop, I have access to the tools and industry contacts that made plating an attractive and affordable option. Not the normal kind of aluminum electroplating, but copper and nickel plating. I spoke with a local plating company who regularly does plating and conversions for the shop. He would be able to put on a thick copper coating, then nickel. The problem with using nickel is that it is one of the four room-temperature metals that are ferromagnetic, something we don’t want in a turntable (and the reason there is a TD124 and a TD124mkII).

The solution will be to use either electro-less nickel plating, known as EN to platers, or nickel-silver (also known as German silver; though it looks similar to silver, it contains no silver). The electroless nickel contains phosphorous which, when making up 11-14% of the alloy, makes the alloy non-magnetic. Nickel-silver, widely used for instrument keys, brasswind and woodwind instrument bodies, resonator guitars, and frets, is primarily copper with nickel added. The result is a metal that is much tougher than copper, looks similar to silver and is highly resistant to corrosion. Also, since it is mostly copper, it is non-magnetic. Unfortunately, I don’t know if I can have something plated with nickel-silver. I’m still investigating at the time of writing.

What are the benefits? Obviously, you don’t see too many shiny metal-plated turntables. Because the chassis will be more electrically conductive, it should allow electrical fields to drain to earth more efficiently. Before I reassemble the table, I will chase the threads of the chassis with a tap, partially exposing the base copper plating, which is more conductive than the nickel layer. The result, if I am lucky, will be a lower noise table due to better conductivity and partial shielding from the motor. That’s the hope, at least.

The first step was to sandblast the chassis to get rid of as much paint as possible. It took about 15 minutes to strip the chassis bare of its mangled paint job. Under the nasty paint was some decent metal, though some nicks and dings were still visible. This meant time with the bench grinder (green oxide buffing wheel), angle grinder with fine grit wheels and maroon-colored fine-grit aluminum-oxide industrial-use Scotch-Brite pads for final smoothing. (That’s the way I like it Soldier! –Ed.) Even if there hadn’t been dings, you should use a Scotch-Brite pad to smooth the finish after sandblasting. If you don’t, you might get a satin finish from the tiny indentions left behind from the blasting process.

That’s it for now. The next installment should cover the plating process.

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