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Thorens TD125 MKI Description

Author: Bushman

General

The TD125 discussed here came without a factory fitted arm and therefore no arm lift mechanism is fitted. The arm fitted on the picture is the Black Widow GF and on there a Shure V15VxMR cartridge is fitted.

The cabinet is DIY and no special precautions were taken to purpose build it for low resonance as it is believed that the TD125 is so well built that the cabinet does not influence its performance.

With this article I will discuss how to tune the suspension, how I restored the main bearing and included is number of pictures showing various parts of the TD125. I do not regard myself as an expert on the TD125 and therefore any comments are welcome.

Fig 1 (above)

 

Fig 2 (above)

Figure 1 & 2 show the basic fitting arrangement of the arm board. Thorens supplied the arm board, prepared for the Black Widow on this turntable. The arm board is made from plywood with no special modifications. It will be easy for the DIYer to make these arm boards or to try different materials. The arm board is fitted to the top plate with three screws one on each of the fingers as shown in figure 1.

Fixing the platter bearing

During initial listening sessions I realized that there is a noise coming from the turntable, clearly audible in-between cuts or quite passages on the LP. The noise was only audible with the stylus in the groove and with the platter turning. It had a mechanical sound to it and sound like something was scraping, at first I thought it was the motor. Removing the belt and spinning the platter by hand revealed that the sound was coming from the platter.

Fig 3 (above)

Removing the sub platter from the bearing assembly clearly showed how the spindle shaft was damaged as a result of rust. The shaft was pitted on the upper part closest to the platter part itself. The damage was not extensive but enough to result in a noisy platter bearing. The bearing found on the TD125 is of very high quality with extreme small tolerance. Without searching for a replacement I started with the repair procedure. I can not guarantee the results, but it is worth the try and it will cost nothing.

I used steel wool to gently remove the rust marks from the shaft. This took time as one has to be very careful and patient, only the part where the rust is present should be treated. There after I carefully polished the shaft again with a good polish, like Braso.

I did not attempt to repair the copper or brass sleeves inside the bearing housing. I then cleaned everything and re-fitted the shaft into the bearing sleeve using thicker graded oil.

The bearing still has a small amount of noise, but the more it runs the better it becomes. I have tried a damped outer platter on the TD125 also with great results. It easily reduced the audible noise by 50%.

Tuning the suspension on the TD125

Similar to the TD16X series turntables the TD125 also use the principle of the sub chassis resting on top of the springs. The configuration of the spring and sub chassis assembly between the TD125 and the TD16X models, however, are very different. The TD16X models have a shaft fitted to the top plate and the spring/sub-chassis assembly then hangs from the top plate. On the TD125 the spring is seated on a plate inside the turntable and the top plate then rest on top of three springs.

 

Fig 4 (above)

 

Fig 5 (above)

Interesting to note from the above pictures is the hole next to each springs. Figure 6 show the bottom side of the top plate and next to each spring rubber or grommet a small shaft is fitted. This shaft goes through the hole next to each spring as showed in figure 4. It then is fitted with a rubber sleeve and a nut at the bottom and the purpose of this shaft is to secure the top plate onto the rest of the turntable. Enough free space is available when the chassis is correctly adjusted for these shafts not to touch the plate inside the turntable. This is also very important as when one of these shafts do make contact with the plate inside the turntable one will not be able to correctly adjust the suspension and it will kill the bass performance.

Have a close look at the spring next to the motor in figure 4. I do not know if this is how it should be or if it is only like that on the TD125 I have. This spring is bent a little in order to produce a "side" force when the suspension is adjusted. I found this to be very important when fine-tuning the suspension. This action is similar to when the wedge pieces are fitted to the bottom of the springs of the TD16X models.

Fig 6 (above)

Fig 7 (above)

The spring is seated onto the white knob or part as shown in figure 5. This white part is also shown from the bottom of the turntable in figure 7 and is used to level the top plate.

Elements to consider when tuning the suspension are the tone-arm cable, the belt and the "bent" spring next to the motor in figure 4. The three springs are used to level the top plate and therefor the platter and said elements are then adjusted to correctly position or align the top plate. These said elements are also used during setting up of the suspension to achieve the correct vertical bounce.

To start off, I added a bit of fat to the inside of the white adjuster knobs, to make the spring slide inside the knob when adjustments are made. I then adjusted each spring to correctly position the top plate and to get it 100% level. The difficult part is then to correctly align the top part in terms of the cabinet and in terms of bounce. To achieve this the bent spring must then be rotated step by step and when in the correct position it will counter the effect of the tone-arm cable and the belt.

The TD125 has a much nicer, accurate and smoother motion on the suspension than what I could achieve in the general on the TD16X models. It is, however, a pain to achieve this and much patience is needed.

Fig 8 (above)

Last word and comments

The TD125 is indeed a lovely turntable, I would not claim it is up there with the best of them, but well tuned and cared for it will outperform many new and more expensive turntables today.

Its character is refined and even a little laid back if one can express it that way. This attribute of a perceived laid back presentation can often be associated with the better quality turntables IMHO. Speed stability is impeccable and motor noise is virtually non existent. The platter as mentioned before can irritate as a result of ringing noises during playback. Using a cork mat does help a lot in neutralizing the platter ring. Keep in mind that any attributes described here is with the Black Widow fitted and using the Shure V15VxMR. I noticed that the TD125 has deep and powerful bass, deeper than my TD166 ambience for example. The bass on the ambience is dryer and better defined in general and more neutral than on the TD125. I can picture the TD125 to be a powerful performer on bass when it is tuned well and tweaked a little. Midrange performance is not forward and treble is well extended with lots of detail, which shows me that the basic design if the turntable is good and well implemented. I have also found that when the suspension is correctly tuned and the arm and cart is correctly installed that the TD125 is very strong on imaging and building a realistic sound stage. The TD125 does not only out performs my CDP it also kills it in the process.