Thorens TD-150 Rebuild Part Two, Project Maple

If you haven’t yet read Part One of this series, please do so now. Herein we will cover the build of a relatively stock Thorens TD-150 MK II turntable, though in a custom Maple plinth to Linn dimensions. Should you wish to do this yourself, please do view the rest of the series and this post covering the LP12 Plinth Dimensions.

We start with a TD-150 that looks as though it has already seen a transformation or two. This model previously had a factory-fitted Thorens arm, as it has the arm lift knob and a couple of remnants of that mechanism still in place.

It’s looking a bit sorry for itself, however. The top trim is no-longer adhered and the plinth is less than ideal. The baseboard is a poor fit and the deck, which would once have held pride of place in a ‘70s audiophile system, looks more like a DIY hack job gone wrong. We can do better than that.

I mercilessly tore the deck apart, ditching the plinth and old arm board. The motor, top plate and sub-chassis remained, as did the sub platter and outer platter which were in nice condition. The deck even had the original mat and 45 RPM adapter.

I cleaned up the parts with Meguair’s NXT Generation all metal polish. This is wonderful stuff which isn’t too abrasive and can be applied using a microfibre cloth and very little elbow grease. The odd spot of corrosion and any surface marks were sanded to 180-grit and several coats of polish were then applied before the parts were buffed to a shine.

Now for a new plinth. The plinth was constructed from 28 mm Maple and built to Linn LP12 dimensions, though the cutout for the top plate was made 0.5 mm deeper to accommodate a stock TD-150 top plate. The plinth is mitred and glued with PVA wood glue and no additional fasteners used in its construction.

I decided not to rebate the triangular braces. They are cut from scraps of the same material and are significantly thicker than those of a Linn plinth. They were glued in place while the plinth was setting and helped to keep things square. Some cuts were made in their outward-facing edges to ensure clearance for the speed mechanism and arm.

The baseboard rebate is 10 mm, as I had intended to use acrylic for the baseboard. I instead went for a plywood shower panel, which is laminated on both sides and is approximately 10.5 mm thick, ideal for our needs.

A 24 mm Forstner bit was used to sink the inserts for the feet, which were then knocked into place. The same Forstner drilled access holes for the 3 suspension adjustment bolts and a hole through which to drop the arm cable.

The top plate was secured in place using 3.5 x 20 mm stainless steel wood screws so as not to risk a reaction between metal and wood, though is is usually only a consideration with Oak. Additional holes were drilled to provide a firmer fixing to the plinth and minimise rattling and loose spots. These, and the original holes, were countersunk with the tip of a 12 mm drill bit to sit the screws flush with the plate, allowing the decorative aluminium trim plate to be secured with double-sided adhesive tape as in the original Thorens design.

A new plate was cut from 1 mm sheet aluminium using the old plate as a template. With the plate sandwiched between 4 mm plywood, straight cuts were made with a sliding mitre saw and the large circular cutout made with a jigsaw fitted with a metal cutting blade. The only feature this new plate lacks is the lettering for the power / speed dial, but that is a minor inconvenience. Right is 45, left is 33 and the middle position is zero or off.

An arm board was machined in maple at just over 12 mm in thickness. It was bolted to the sub-chassis using 4 30 mm stainless bolts. A 23 mm hole was drilled at a distance of 222 mm from the centre spindle to fit a Rega arm. A stock Rega RB202 was selected and bolted into place with 50 mm M3 bolts, which allow for VTA shims in future should they ever be necessary. The cable drops through a hole in the baseboard directly beneath.

The electronics are identical to the Thorens design, albeit with more modern components. A 0.01uF suppression capacitor sits across the switch and there’s a 0.33uF motor phase capacitor, both class X2 rated for use at mains voltages and both far higher than the maximum of 250V they will see under normal use. The dropping resistor was replaced too with a 5600Ω (5K6) wire wound resistor, and is used to drop the 220-240V mains supply down to the 110-120V for which the motor is designed. A standard terminal block was used, exactly as in the original TD-150. I could (should) have added an internal fuse too, but there’s a fuse in the plug and as this was clearly good enough for the past 5 decades, it’s good enough now.

Balancing the suspension is a subject I discuss in Part Four. I made a frame to facilitate this, essentially an open-top table in which the turntable plinth can sit. The frame is then levelled to level the edges of the plinth, and the underneath can be accessed to tweak the suspension.

In terms of things we’ve changed from the stock configuration. The plinth has obviously been replaced, as was the decorative trim plate covering the top plate screws. All bolts were replaced with Allen head equivalents, and the spring bolts extended to 60 mm to accommodate different springs as my originals were too worn to be used. The electronics were replaced but with components of an equivalent electrical specification. The arm is obviously not a stock Thorens arm, but neither of my decks came with one of those. And the arm board is wider.

Aside from this, our top plate, sub-chassis, platter, sub platter, bearing and motor are original – in short, most of the components responsible for the deck’s performance. Even the oil is as original as possible. I used Mobil DTE Medium VG46 turbine oil, which is a close modern replacement for the original oil used by Thorens. This was used to lubricate both the platter bearing and motor.

And there we have it, a stock TD-150 transformed but with its original charm intact. Look out for Part Three in which we’ll build the AAP12 and see just how far the humble TD-150 can be taken.