Funny things people notice about Thorens platter bearings.
***On the belt driven models***
Even though the suspended belt driven layout remained present on most of Thorens' turntables from the sixties on into the 21st century, many detail changes appeared throughout the various model runs. This page, at first, will attempt to document the variations seen in platter bearings and the sub-platters starting with the TD150. Perhaps as information is gathered some light will eventually be shed on why some of the more curious detail changes appeared.
There is a similarity of platter bearing design and manufacturing practice between several different models in the Thorens lineup. We are, after all, looking at a mass production method. We do see quite a lot of parts interchangeability yet there are also numerous detail differences in material and size that preclude interchangeability.
To save bandwidth, many of the photos on this page have been thumb-nailed. To see the full size image, simply mouse click that image.
First came the TD150
Above: TD150 spindle shaft. Features include; die-cast zinc sub-platter, 10mm spindle shaft with captive ball bearing tip.
Above pic: looking down on the TD150 without its platters or armboard.
Above pic: A pair of sub-chassis frames. Left, TD150 sub-chassis frame. Right, TD160 sub-chassis frame. Notice the same platter bearing housing being used in either frame. This 10mm bearing housing was also used on the idler driven TD135. The TD160 frame was used throughout on the TD16x models up until the last of the TD166 models in the late 'nineties.
TD125 Mk I, early
Above photos: TD125 Mk I sub-platter and bearing. For the sub-platter features include; die-cast zinc sub-platter, 10mm spindle shaft with captive ball bearing tip. (same as TD150) Note also the strobe ring staked into place at the inner rim of the sub-platter. This was not used on the TD150.
For the bearing housing, features include: a die cast metal housing with pressed in bronze bushings. Design is flanged and drilled for machine screw fasteners. The bottom thrust plate/pad is permanently swaged into place at the factory. This housing is not designed to routinely have its bushings and thrust pad replaced.
Above: upper and lower views of the TD125 Mk I sub-chassis frame. This example is machined for the earlier flanged type bearing.
mk1 below, mkII above
Above photos 1a and 1b: For comparison....a TD125 mk2 sub-chassis with bearing. Above photos 1c and 1d: a TD125 mk1 sub-chassis with bearing. Note the 3-screw configuration of the mk 1 whereas the mk2 is pressed in and has no retaining screws. Later mk1's also used the press-fit bearing.
Above: a TD125 sub-platter with solid spherical tip. It could be a Mk II or perhaps later in the Mk I production run. The TD125 models used a strobe ring as part of their pitch control system. In this photo the method of attachment for the strobe ring can clearly be identified as being 'staked'. A punch has been used around the perimeter to deform the zinc metal over the ring, pressing it firmly against a machined shoulder.
Later in the production run, the ball bearing tipped shaft was replaced with the solid spherical tipped shaft. The flanged cast bearing housing was replaced with a thinner machined steel housing as was used in the TD150 and TD160.
The new TD160 also came equipped with the solid tipped shaft and used the same bearing housing as seen in theTD135, TD150 and later TD125 MKII. This allowed Thorens to use the same shaft and bearing housing on both the TD125 Mk II and the new TD160. An apparent cost savings in manufacturing time, labor and materials. Whether or not there was any sonic loss as a result is unknown but it would appear the TD125 Mk II became a little less expensive to manufacture.
Above pic: upper and lower views of the TD150 bearing. Size is 10mm. This was to become the standard bearing used in the TD125 Mk II, Early TD126, TD160, TD145 and the TD147. There was a 7mm version of it as well for theTD126 Mk III, TD165, TD166, TD146 and others. Fit up in the sub-chassis frame is via interference of size (press fit). One example from a TD160, after I disassembled the housing from the sub-chassis pan, showed evidence of an adhesive being used. This is not consistent, however. Others report of no adhesive.
Above pic: looking down into the TD150 bearing. A fiber-optic light tube is used to illuminate the interior. The layout is comprised of two bronze bushings pressed into the steel housing. The flat thrust plate at the very bottom takes the entire vertical load of the platter system. This assembled weight is concentrated at the point of contact between the spherical tip on the shaft and the flat plate of the bearing. For lubrication, oil is contained within the cavity. This example shows some loose debris which was later cleaned out painstakingly with a Q-tip, and then re-lubed before returning the bearing into service.
Note: Dimensionally, both platter shaft types are functionally identical. In other words a ball-tipped TD150 sub-platter may be used in a TD160 and retain correct vertical location of its platters. It is less likely that an early TD125 flanged bearing housing would be used on a later model Thorens as that would require a careful and accurate machining operation beyond the capability of the casual diy'er. But this could also be done.
TD160 Mk 1
TD160 sub-platter. Features include: die-cast-zinc sub-platter, 10mm spindle shaft with solid spherical tip. Note also the missing strobe ring. The TD150, TD160, or any of the TD16x and TD14x series models came without pitch control and therefore no strobe.
Above: a TD160 Mk II. Features include die-cast zinc sub-platter, tough resin safety catch, 10mm spindle shaft with solid spherical tip. Pic above and to the right is the bearing housing of a TD160 Mk II, upper view.
TD145: same as TD160. zinc / 10mm solid tip
TD147: same as TD160. Zinc / 10mm solid tip
TD165: commonly a resin sub-platter with 7mm spindle shaft, solid spherical tip but some have been found with zinc/10mm and some with zinc / 7mm and for variation: resin/10mm.
Readers notes from Ewan Campbell:
From my taking the bearing off a TD126 Mk2 and replacing it with one off a
Same table as TD126 but with extended base and armboard for 12 inch tonearms. On the example Holger has he found a 10mm bearing with cast zinc inner platter. Even though the TD126 MkIII was in production at this time, the TD127 came equipped with the earlier 16-pole AC synchronous motor from the earlier TD126 models, and not the 72-pole DC motor of the TD126 MkIII.
The TD166 most commonly, as with TD165, was equipped with a resin sub-platter, 7mm spindle shaft with solid spherical tip. But as seen below, there were variations.
Above. This example is from a TD166 Mk II. Features include die-cast zinc sub-platter, tough resin safety catch, 7mm spindle shaft with solid conical tip. Compare the material shape at the rim with that of the earlier TD150, TD125 and TD160 sub-platters, a different casting pattern.
Above. Top view to the same TD166 Mk II zinc platter. Clearly this is a different casting pattern from the TD160 units seen above.
Measuring tape indicates the 7mm diameter of this TD166 bearing shaft.
Above: resin, 7mm platter from another TD166 Mk II. Circa early 1980s.
TD166 Mk IV circa late 1990's with resin sub-platter.
Thorens Prestige bearing. Many detail close-up photos courtesy of Rolf Kelch Electronics.
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