Thorens TD125 Motor, speed controller and power supply replacement

Hello All,

I am in need of a new replacement motor and speed controller to replace the stock motor/spc on a vintage Thorens TD125. Premotec and Maxon were both motors I have heard good things about but I have no idea which model would be most suitable and how to go about purchasing/building a speed controller and power supply. I am not interested in the Origin Live motor option as I feel there may be a better solution through purchasing separate high quality parts directly from the mfg. I do not wish to simply replace the stock TD125 motor with another vintage unit as I feel the table is worthy of a much higher quality motor. Ideally, the motor would rest in the same location as the original one within the subchassis with the belt riding on the outside of the inner sub platter. I was not sure if this also played a factor when trying to find a suitable motor but thought I would mention it anyway. My thoughts were the power supply and speed controller would be outboard placement wise, so would not have to worry about fitting inside the chassis or plinth frame.

It would be ideal not to have to mess with the original power supply or internal electrolytic caps, ect. I would much rather go new all the way. :)

Thanks,
Chris
 

Attachments

  • IMG_3753.JPG
    IMG_3753.JPG
    742.2 KB · Views: 527
  • IMG_3766.JPG
    IMG_3766.JPG
    382.9 KB · Views: 483
  • front_top_and_base.jpg
    front_top_and_base.jpg
    66.8 KB · Views: 458
  • base_plate.jpg
    base_plate.jpg
    97.2 KB · Views: 442
  • view hz.jpg
    view hz.jpg
    58.5 KB · Views: 453
I wouldn't bother rebuilding the Thorens motor board, it was an OK design for its day but things have progressed greatly since then.

Unfortunately that isn't the case with the motors themselves, the AC synchronous motors available off the shelf are all basically crap. Amongst their many problems is the use of lots of iron in the stator to increase magnetic efficiency, unfortunately this also causes gross cogging.

What people call a BLDC motor is really a three phase EC (electronically commutated) motor, which is identical to a multiphase synchronous motor. The trouble with these is finding one with an adequate number of poles - since they usually run at relatively high speed they usually have very few pole pairs - the Maxon EC motors mostly have two or four poles. Multi pole motors generally have iron in the stator which brings us back to point 1.

I'll make you a deal : you find me source of ironless BLDC motors with at least 8 poles at an affordable price, I will design and build a suitable supply that has the same footprint as the Thorens supply. The prototype will be yours as a finder's fee.
 
Last edited:
certainly out of my area of "knowledge" ...

(notice I didn't use "expertise" as some might, I've just enough knowledge to be slightly dangerous).

If looking for something suitable for an AC synchronous motor, look at the Hurst motors as well. Good enough for AR and George Merrill (who could easily spec a more expensive motor), good enough for me.

I have one here I am setting up to run-in for a week or two (continuous operation). Then adjust the bearings, etc

In my life, simpler is better. There is some elegance in ultra simple (Zen?) design. Even in interiors, cars, watches, and furniture. (OK and mid century modern via Eames, van der Rohe, and the Scandinavian school of design.

Mark: it depends on what you feel is a reasonable price for a BLDC motor.
 
If looking for something suitable for an AC synchronous motor, look at the Hurst motors as well.

Mark: it depends on what you feel is a reasonable price for a BLDC motor.

My experience with Hurst motors has been very much less than positive. The variation of shaft diameter between samples is such that I cannot obtain an adequate standard of pulley concentricity unless I get each pulley bored specifically for the motor it is to mount.

YMMV etc etc.

I would consider $USD250 a reasonable cost for a motor which met my specs. The offer of a free drive as finder's fee is open to all.

The motor must have:

At least 8 poles.

Ironless stator or stator slotted to achieve detent torque less than 1mNm

Output torque greater than 40 mNm

Shaft diameter between 3mm and 6mm (+/- 0.5% of diameter)
 
Last edited:
I can't say I have any experience (although...)

I recently bought a high torque model, not a "turntable" type. I haven't run it yet.

AR used the 3001-001

They can be very noisy, so do a search for "Merrill motor mods" and see what George Merrill has done to make them much quieter.
 
My solution for my TD 125: I removed all old electric parts and added 1 new pro-ject 20 pole motor with custom electronics base on 2 12 bit DAC and one look-up sine table. For the output drive I use 2 LM1875. If interest I can supply more details.
Cheers
 

Attachments

  • im1.jpg
    im1.jpg
    148.5 KB · Views: 347
  • im2.jpg
    im2.jpg
    163.9 KB · Views: 341
bruno3955
I loved that about using the LM1875! Very clever. Funny, I found recently 6 TDA2030A from a possible dead subwoofer (bad quality on the circuit), which I wondered if I could use it to something else than music...

To bad that I was too late with my idea. I like that: I am not unique. :)
Pictures are always cool. Please? :)
I liked that sinuslookuptable, but wouldn't the resolution be bad? (=not so smooth)

Nanook: Pictures? Pretty Please? High torques are always cool. :)
Chris74 Thank you for these pictures, I have always been curious about Thorens. If' you're ripping out the circuit, can you please post a pictures of the top of it? :eek:

My advice is:
If you're not knowledgable or not wanting to learn more motors or tinkering with them, I recommend to go with a similar motor, running at same speed. There is usually a paper/number on the motor with some information. Google that. You can always experience, but as of now - look what you really want to do/have. Get a 33.33 and 45 rpm measuringpaper to be sure it's rotating at the correct speed. I downloaded it from the internet, so it's free. Sorry I don't have the adress, and I hope that others can point it out.

What's your budget?
Sadly the motors are expensive in the hi-fi world, but it's difficult(?) to find a random motor and connect it without knowledge of electronic and mechanic to make it go at correct rpm. Good luck!

Brushless motors are everywhere:
inside a harddisk is of high quality, I have a few nice one, but they're cogging and maybe too weak. The older one are betterand easier to remove (under 2-5GB), the newer one is more intergrated to the chassis. I haven't bothered to cut it out. I'll try the big rotating wheel from a VHSplayer, it may be a brushless motor. The CD/DVD player has brushless motor - I have few - most of them have 9 stator, with iron and bushings, all of them with cogging. I just keep them for playing. *giggle* :)

Check this out http://www.diyaudio.com/forums/anal...cial-turntable-drive-system-motor-thread.html they know more than me!


Is cogging on the motor really bad? The belt dampens the vibration, the motor have soft suspension, and the LP-platter may be too heavy to even notice the vibration from the motor. Hell, the noises and the good vibration from Pink Floyd may even be worser!

Mark Kelly
My experience with Hurst motors has been very much less than positive. The variation of shaft diameter between samples is such that I cannot obtain an adequate standard of pulley concentricity unless I get each pulley bored specifically for the motor it is to mount.

That sound weirds. How tight tolerances did your pulleys have?
Wouldn't a setscrew solve this? (it's on my Pro-ject motor)

I'll look more at Hurst motors (7.5degree), but I don't see them as awful, they seems similar of my Pro-ject motor. I putted recently a little dip of teflonlubrication in the brass bearings to reduce friction. (NOT WD40! )
 
That sound weirds. How tight tolerances did your pulleys have?
Wouldn't a setscrew solve this? (it's on my Pro-ject motor)

[/QUOTE]

The pulleys had four setscrews and were machined to an ISO H7 fit by a professional machinist who subcontracts to a well know high end TT manufacturer. The machinist was given a sample motor to ensure that the pulleys were correctly dimensioned. All the pulleys received fitted that motor perfectly but did not fit any of the other motors. I was able to measure the shaft diameter differences using an ordinary Mitutoyo digital caliper.

The results were turned over to the TT manufacturer (for whom I was working as a subcontractor) and he was also unable to make the pulleys fit the motors.

The project was abandonned shortly afterwards.
 
pictures?, How about actual specifications?

LYD42115D
minimum torque holding (oz-in): 4
Minimum Holding Torque (mN-m): 28.2
speed: 250/300
Voltage: 115AC, 60Hz; 220, 50Hz
Winding resistance (Ω): 3700
Rated Ind. (mH/phase):4.7
Capacitor required:.39mF

I think this should be OK, for a synchronous Ac motor.