DIY AC motor control

[karvid]

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.

[Pjotr]

The TD 160 has a 110V AC motor which is wired through a capacitor and resistor to the 220V AC mains in Europe.

A speed controller for that is not an easy matter.

[Mark Kelly]

I have a kit available which does what you want but it isn't easy to build.

You'll have to wait until after vintage.

[faxurda]

Tell me more about this kit I'm interested... for 115volt?

The other solution I founs is the Project Speed Box.

[Nanook]

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

[Pjotr]

I see, a CD-player and huge power amp just to run your turntable

That motor consumes just a few watts … A power wien-bridge oscillator and a 5 – 10 VA mains trannie connected reversed can do the trick as well.

[Nanook]

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

[Brett]

Originally posted by Mark Kelly
I have a kit available which does what you want but it isn't easy to build.

You'll have to wait until after vintage.

Im interested too and in no hurry, so I'll wait for you to post again and get details then. Cheers

[stoolpigeon]

The ancient Audio Amateur PS designed by Gary Galo is easy to make and works well.

I'm fairly sure it uses an XR2206 function generator chip which is listed in my 2004 Jaycar dogalog for $14.

sp

[AndrewT]

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.