Thorens TD125 Motor, speed controller and power supply replacement - diyAudio
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Old 20th October 2010, 06:52 PM   #1
Chris74 is offline Chris74  United States
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Default 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
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Old 21st October 2010, 04:15 AM   #2
kevinkr is offline kevinkr  United States
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You might want to investigate some of the TT motor controller stuff Mark Kelly came up with. I think some of it is here on diyaudio..

Seems like a brushless dc (hall effect) motor might be worth checking into..
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Old 21st October 2010, 05:27 AM   #3
Chris74 is offline Chris74  United States
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Thanks, not familiar with the Mike Kelly motor controllers but will search the archives to see what I can find.

Any suggestion as to which brushless dc to look at - Premotec?
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Old 21st October 2010, 04:44 PM   #4
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Chris74 View Post
Thanks, not familiar with the Mike Kelly motor controllers but will search the archives to see what I can find.

Any suggestion as to which brushless dc to look at - Premotec?
Premotec would certainly be one I would look at, but there are probably some good ones from Papst, and micromo/portescap as well..

Did you see my PM?
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Old 21st October 2010, 10:18 PM   #5
Chris74 is offline Chris74  United States
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Yes, just read your PM, reply sent. I knew about Pabst but not Micromo/Portescap, will look into them, thanks. I seem to be able to find what I feel would be suitable replacement motors but not the power supply/speed controllers.
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Old 22nd October 2010, 04:34 AM   #6
Chris74 is offline Chris74  United States
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I was thinking, maybe if I can find a drop in replacement motor I could rebuild the stock TD125 motor controller board/ps. Might this make more sense?
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Old 22nd October 2010, 09:15 AM   #7
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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 by Mark Kelly; 22nd October 2010 at 09:23 AM.
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Old 22nd October 2010, 07:01 PM   #8
Chris74 is offline Chris74  United States
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Mike, appreciate the information and your opinion on the matter. Thanks for the generous offer but honestly, I really wouldn't know where to begin to search for such a motor.
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Old 22nd October 2010, 09:54 PM   #9
Chris74 is offline Chris74  United States
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Mark, sorry for the typo
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Old 23rd October 2010, 08:10 PM   #10
Nanook is offline Nanook  Canada
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Default 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.
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