Thorens speed control

[Bazil]

I would like in the new year to remove the mechanical speed adjuster from my Thorens TD160 and replace it with an off-board control.
Does anybody know of a thread for this, I've tried searching.
cheers

[bobbasrah]

Barry, I suspect you may find some under Linn or similar models of Thorens, google it as I did with variations.
There are two versions that I found previously, both DIY frequency control over 110v ac, similar to the Origin Live design.

As I was initially looking to drop the voltage on a 160 when I came across these PSUs, but they as they were geared to what you were after rather than voltage reduction I paid them no mind. I'm tempted to go a similar route, but the detection side seemed a mite complicated.
If I find them again I'll post back.

[keiths]

There's a DIY speed controller at the final stages of development over at Lenco Heaven (PCB has been designed and a few members are currently beta testing and ironing-out some issues). This will allow voltage reduction and one, two or three adjustable speeds depending how you build it.

http://www.lencoheaven.net/forum/index.php?topic=4406.0

[Reid Malenfant]

The problem with voltage reduction is a huge drop off in torque, really the frequency needs altering to get the best out of a syncronous motor.

It'd still work mind you, just not as well as changing the mains supply frequency.

It shouldn't be too difficult to cobble something together with an low distortion oscillator (with a switch to control the frequency), an amplifier & a capacitor & transformer to step up the output to 230V

[keiths]

Hi Mark,

The Lenco Heaven one works by changing the frequency. It also (optionally) allows voltage reduction to enable the optimum balance between motor vibration/noise and torque to be found.

[Reid Malenfant]

Ah, much better Cheers for putting me right, I guess I should have taken a look before typing

[DSJR]

S'all right Mark, and thanks all for the links, as I should like to have a go at some point..

The synchronous motors Thorens used gave just about the correct torque in their designs I thought, but an external smoothing and filtration transformer a la Naim Armageddon "may" be all you need. Don't forget the circuit used in the TD125 series either, as this allows smooth motor rotation and is three speed (I'm sure the 16rpm could be dropped and a 78 option introduced if necessary, though not sure how the belt itself would cope?)

The Lingo used to give full power to allow starting, which was then cut back to around 70 or 80V for running proper, this removing much of the motor vibration from the deck-plate. I don't honestly think the TD150/160 series suffered so tbh, so a simple frequency shifter for the two speeds would be ideal.

Re Lenco's. I now have my GL78 project to start in the new year and a facility to safely take the motor torque back a tad would be ideal for these as previous attempts with fixed inline resistors reduced motor borne "rumble" by around 10db I believe, a useful amount on an already fairly quiet motor system of the type. The only Lenco difference I found (nothing sonically to me) was the sharp "kick" on startup was reduced to something more idler-friendly I remember...

[Reid Malenfant]

Hi Mark,

The Lenco Heaven one works by changing the frequency. It also (optionally) allows voltage reduction to enable the optimum balance between motor vibration/noise and torque to be found.

Just took a look & it's kind of what I fugured, I couldn't find a circuit diagram though

Would have been nice to see that in all honesty

It would have been nice if they had used the output of the transformer as part of the feedback loop to gain rock solid voltage stability. That could easily be implemented with an extra opamp between the oscillator & amplifier input. Obviously this wasn't done or the output voltage wouldn't have dropped as it appeared to.

Why didn't the guy have a frequency counter to accurately set the thing up???

Still a noble effort none the less

[DSJR]

Now THAT's a Christmas challenge Mark - and if you're serious about giving up smoking, then it might be something to keep you occupied

[keiths]

Just took a look & it's kind of what I fugured, I couldn't find a circuit diagram though

Would have been nice to see that in all honesty

I think Nigel wants to get it all pretty thoroughly tested and idiot-proof before publishing the circuit and parts list - many of the people who have expressed an interest in building it on LH have done little or no electronics DIY before and safety etc seems to be his overriding concern - so he doesn't want any of them trying to build it before he's done comprehensive and easy to follow instructions complete with appropriate safety warnings and so on.

As to the circuit design choices etc. - I've no idea...