Monday, 14 November 2016

Building A Custom Plinth For A Thorens TD 150 Mk II


About eighteen months ago I picked up a shabby-looking Thorens TD 150 Mk II turntable. It came with an SME 3009 Series II Improved tonearm (fixed headshell) which was missing its rider rod, the rider weight and fingerlift. I paid £210 for the whole shebang - about what you might expect to pay for the arm on its own. I soon got hold of the missing components for the arm, but the turntable sat neglected in its tired, ugly plinth until May of this year when I finally gave in to the urge to prod it with the pretty stick.

Vendor's ebay photo of my unloved Thorens TD150 MkII

The original plinth on the Thorens TD 150 is, to my eyes, inadequate - both structurally and aesthetically - for such an iconic turntable. This particular one was in a particularly scruffy state. I figured that, if I could make a picture frame (which I can), then making a new plinth for a turntable shouldn't be beyond my limited DIY skills. Next stop, ebay, where I found some pre-planed lengths of American Black Walnut.

20 mm-thick American Black Walnut

Concerned that I'd forget which parts of the turntable's innards went where when piecing it all back together, I took dozens of photos of each component from every conceivable angle before beginning the process of dismantling the turntable. You can't be too careful!

The TD150's innards

It took me a while to work out that the screws that secure the turntable to the plinth are located under the aluminium top-plate on the Thorens. And even longer to find out how to remove the top-plate to get at them. Uncharacteristically, I didn't resort to brute force, but searched patiently online for a solution. It turns out that the upper and lower plates of the TD150 are held together with double-sided tape. Its grip showed no signs of having weakened with the passing years, but heating the aluminium with a hairdryer liquefied the adhesive on the tape and allowed the two plates to be slowly and carefully prised apart. Slowly, because the thin top plate could easily crease or bend if rushed.

Using a hairdryer to loosen the grip of double sided tape

I fitted a new blade to my mitre saw in anticipation of the walnut being heavy going, but nothing could have prepared me for the iron-like density of this timber. This is why the DIY gods invented power tools - shame then that my mitre saw is powered by sweat and expletives. It did the job though - eventually. A framers' guillotine was then used to remove wafer-thin slices of walnut from the mitred timber to ensure a good clean, accurate join, and the parts were glued and clamped.

Assembled plinth glued and clamped

For simplicity's sake I made the plinth with the same internal dimensions as the original, albeit with higher (90mm), and thicker (20mm) sides. With hindsight I should have made it a few centimetres wider to accommodate a larger armboard and to give the SME tonearm a bit more room to breathe, but that's a minor quibble.

Once the main body had been assembled and clamped, I used the triangular off cuts that resulted from cutting those 45 degree mitre joints to brace and strengthen the plinth. These were cut to an appropriate length and glued in place. After allowing 12 hours for the glued joints to dry, using the layout of the original plinth as a guide, I cut lengths of 10mm pine stripwood and glued and nailed them in place to provide the necessary support for the top-plate. Once dry, I dropped the turntable into its new plinth and - surprise, surprise - it fit.

Trying the plinth for size

The next stage was to use fine sandpaper and wire wool to give a really smooth finish to the timber. Once the surface was prepared, I applied natural Danish Oil with a cloth to bring out the beauty of the grain. I allowed six hours' drying time between each of the five coats and used a fine sandpaper on the plinth between applications, finally buffing with a cloth to give a warm satin finish to the wood.

Braces and batons

Corner brace

Building up the layers of Danish oil

I replaced the original flimsy baseboard with a piece of 6mm MDF. This improves the structural integrity of the plinth and, as a result, the sonics of the turntable. I could probably have used an even thicker piece of MDF, but that's something that I can easily change down the line. I discarded the original black rubber washers that were masquerading as feet and opted instead for height-adjustable conical metal spikes. They look great and make the turntable easy to level.

Conical turntable isolation foot

I drilled two holes in the rear of the plinth for the power lead and arm cable. On the original plinth the leads were fed through holes in the baseboard, but I was looking for a tidier and more elegant finish. Then I went to work on the platter,  giving it a thorough going over with T-Cut metal polish before buffing with a soft cloth. I opted to keep the original arm-lowering knob on the turntable, even though it's disconnected and surplus to requirements, because, well, why not! It lends balance to the over-all look.

Ideally, I would like an armboard made from the same walnut as the plinth. I've earmarked a piece with a particularly attractive rippled grain, but I don't have the right tools to accurately cut the timber. For now, I'll make do with the original armboard, even though it's looking past its best - not helped by the fact that I used acetone to clean off some dirt and sticky residue and removed part of the black lacquered finish in the process!

Piece of walnut earmarked for the new armboard (with the original)

I recently acquired a new platter weight, with integral spirit level, from a seller in Germany. I had to adjust the suspension on the Thorens to allow for the added weight, but it sets the turntable off nicely and tightens up the sound.

Platter stabilizer weight with integral spirit level

The SME came fitted with an ADC 10E MkIV moving magnet cartridge when I bought it. This is a great little cart, but I have no idea how many hours are on it, or how it had been treated by its former owner. The fact that he was using the arm without the rider weight may hint at the stylus having uneven wear. Being incapable of leaving my equipment alone (!), I had to try a Moving Coil cartridge on the Thorens, just for a comparison. Unfortunately, it sounds so damned good that I don't want to take it off. I had intended using it with my Linn Sondek, but am having second thoughts now. The cartridge in question is an Audio Technica AT-F5 OCC. And it's lush!

Audio Technica AT-F5 OCC and disc stabilizer

At some point, I plan to have a  Perspex dust cover custom-built to finish the turntable off. For what was intended as a cheap back-up turntable to play some of my more beat-up records, this is turning into a rather serious project. The performance of the TD150 since I nursed it back to health is beyond anything I could have imagined. I'm beginning to understand why so many people hold these turntables in such high regard.

Linn Sondek LP12 alongside Thorens TD150 MkII

5 comments:

  1. That looks superb! Far better than the original plinth, it really injects some vitality back into the player that's for sure.

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  2. Thank you. There is a school of thought that believes it's sacrilege to mess with the originality of a turntable like this, but I'm not convinced that original always mean better. I can't believe how great this deck looks and sounds now.

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  4. Yes indeed sir, the Linn is the copy, the Thorens the original.

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