DIY AC motor control

karvid

Member
2006-11-18 9:58 pm
Hello,
I have been searching for a motor control that I can use in my Thorens TD 160 Super. I beleave it has an 16V AC motor.

Is there a diagram for a get a good PSU and if possible get possibility to adjust speed.

46fc_2.JPG


:confused:
 
not an AC controller ...

But a means to control an AC synchronous motor.

Either use a signal generator, or make your own . Run the generated signal through a big power amplifier, full tilt. A recorded cd + power amplifier could also work.

Just always have a 0 signal to start, and a 25 minute 120 Hz or 110 Hz (depending on what frequency your motor is expecting to see---I get 117 Hz at my house....) signal through the amplifier. Perfect use for an old mono SS amp or build yourself a single channel T-amp or similar. Just make sure that the amplifier output exceeds the turntable's requirements.

If speed is "off" just re-record a 121 Hz signal, and so on.

I've never built a setup like this, but really self explanatory. A little "brute force", and certainly not elegant as a solution --- but a solution, as long as the amp runs very quiet.

You may also be able to build an oscillating circuit at the correct frequency, using computer type (and speed) crystal oscillators. Then perform "divide by 2" schemes to get you where you need to be.

The cd solution seems the easiest to me.

If MK has a solution, I know it would be more elegant , and nicer to implement than either of my suggestions.



stew
 
my suggestion was....

an easy to implement one. It allows for a change in reference voltage and frequency, something that does determine the speed at which a sychronous alternating current motor depends on.

That's all.Depending on the time of day, the frequency of the mains and voltage can shift 4-7% (so sez the local utility).

A crystal oscillator may be the simplest solution yet.

As far as a few watts, true, but not necessarily low voltage, and that's what most amps are , voltage amplifiers. The infamous Linn Airpax motors need at least 72 volts to start and stay quiet.


stew
 
Hi,
TV crystals (around 4MHz & 6MHz, can't remember the exact F) divide almost exactly to generate 50Hz and 67.5Hz.
The motor is likely to be under 10W and a 50W amp driving a small mains transformer back to front will give you around 110Vac.
The TD150 motor ran well at 80Vac but would not self start below 90Vac, so I settled on 100Vac.
 
I normally have an ad on the classifieds at Audio Asylum but I have withdrawn it whilst I am busy with vintage.

It will be back up when my workload reduces to sane levels - I expect that to be sometime in late April. I have 42 wines actively fermenting at the moment so I'm as busy as a fly in a bottle.

I don't broadcast my email address due to spambots.
 
Hi
I built a power supply using two crystals. It works really well. It is speed stable and provides great base control in the music.

I can not remember the actual values of the crystals at the moment but if you want to build this type of supply I will take off the top cover and check the crystals values.

Don
 

karvid

Member
2006-11-18 9:58 pm
AMV8 said:
Hi
I built a power supply using two crystals. It works really well. It is speed stable and provides great base control in the music.

I can not remember the actual values of the crystals at the moment but if you want to build this type of supply I will take off the top cover and check the crystals values.

Don


Thanks AMV8,
have you got any diagram showing the complete PSU?



:D
 
karvid

I do - somewhere. But I built this some 10 years ago and I will have to look for it.

Actually I built two and they are still in use on rock turntables. The change they made when fitted was probably the biggest change I have heard form any improvement I made to the turntable.

I live near Max Townshwnd who designed the deck and he agreed that ac speed control does make a great difference.

Don
 

karvid

Member
2006-11-18 9:58 pm
AMV8 said:
karvid

I do - somewhere. But I built this some 10 years ago and I will have to look for it.

Actually I built two and they are still in use on rock turntables. The change they made when fitted was probably the biggest change I have heard form any improvement I made to the turntable.

I live near Max Townshwnd who designed the deck and he agreed that ac speed control does make a great difference.

Don

Thanks,
I really appreciate your help. :)

//Kenneth
 

Brett

Member
2002-01-07 6:02 pm
AMV8 said:
Actually I built two and they are still in use on rock turntables. The change they made when fitted was probably the biggest change I have heard form any improvement I made to the turntable.

I live near Max Townshwnd who designed the deck and he agreed that ac speed control does make a great difference.

Don
I have a Rock in storage (vinyl is out for the time being) as well as the Merlin PS for it. Makes a difference. Terrific TT too.

I also have a 240V rim drive design I want a PS for and Mark's solutions are tpically well thought out, so I'm interested in that rather than merely cloning the Merlin.
 

karvid

Member
2006-11-18 9:58 pm
Brett said:
I have a Rock in storage (vinyl is out for the time being) as well as the Merlin PS for it. Makes a difference. Terrific TT too.

I also have a 240V rim drive design I want a PS for and Mark's solutions are tpically well thought out, so I'm interested in that rather than merely cloning the Merlin.


:D
I have two TT's I want to try with a precision PS.
The first one is an Thorens 160 Super:
[IMGDEAD]http://user.tninet.se/~pst442t/vinyl/rega_1x.jpg[/IMGDEAD]

and the second is an Opus Continuo. An 23 kg heavy player with AudioCraft tonearm:
[IMGDEAD]http://user.tninet.se/~kaw434x/hifi/hela.jpg[/IMGDEAD]
[IMGDEAD]http://user.tninet.se/~kaw434x/hifi/Benz_2.jpg[/IMGDEAD]