Regards all.
I own a near 30 years old Well Tempered turntable, original model with square motor base. These turntables use Hurst motors equivalent to the current Hurst PB-3230-001, a high 38.8 mN-m torque, 600 rpm, 2 phase, 115v 60Hz, 10 watts A/C synchronous motor, which are most similar to the one used by VPI in their SAMA.
Sometime ago I noticed that the table was running slow and embarqued in a process to get the table running at the correct and stable speed.
To that end I acquired scobham’s Zeus motor controller and built a 25 watts 2 channel D Class amplifier. Similar to Pyramid’s controller and amplifiers project but with feedback loop. Great kit super well recommended, and Stephen's support has been great.
Anyways, I have been able to get the motor running quite better than originally, but as Pyramid has noted on several strings and postings, apparently the 10 watts Hurst motor does not lend itself to very precise, constant speed operation, and no matter how much control and adjustment is made to voltages, frequencies and PID parameters, the motor’s speed still oscillates more than say Premotec / Airpax/ Phillips/ Allied Motion motor used on may turntables.
I am considering changing the motor for another model, but the Allied Motion 990411131813 motor used on may turntables has a much lower torque capacity (I believe of 20 mN-m) than the Hurst and I believe insufficient to consistently start the platter.
I have also read of Pyramid’s implementation of the 3 phase dc motor and control, and I am considering it, but wish to know if there are other 2 phase A/C synchronous motors I can consider.
So…. Beside the Premotec / Airpax/ Phillips/ Allied Motion motor and the Hurst motors, which other motors are used on turntables or recommended to use substituting my current 10 watts Hurst?
Thanks.
I own a near 30 years old Well Tempered turntable, original model with square motor base. These turntables use Hurst motors equivalent to the current Hurst PB-3230-001, a high 38.8 mN-m torque, 600 rpm, 2 phase, 115v 60Hz, 10 watts A/C synchronous motor, which are most similar to the one used by VPI in their SAMA.
Sometime ago I noticed that the table was running slow and embarqued in a process to get the table running at the correct and stable speed.
To that end I acquired scobham’s Zeus motor controller and built a 25 watts 2 channel D Class amplifier. Similar to Pyramid’s controller and amplifiers project but with feedback loop. Great kit super well recommended, and Stephen's support has been great.
Anyways, I have been able to get the motor running quite better than originally, but as Pyramid has noted on several strings and postings, apparently the 10 watts Hurst motor does not lend itself to very precise, constant speed operation, and no matter how much control and adjustment is made to voltages, frequencies and PID parameters, the motor’s speed still oscillates more than say Premotec / Airpax/ Phillips/ Allied Motion motor used on may turntables.
I am considering changing the motor for another model, but the Allied Motion 990411131813 motor used on may turntables has a much lower torque capacity (I believe of 20 mN-m) than the Hurst and I believe insufficient to consistently start the platter.
I have also read of Pyramid’s implementation of the 3 phase dc motor and control, and I am considering it, but wish to know if there are other 2 phase A/C synchronous motors I can consider.
So…. Beside the Premotec / Airpax/ Phillips/ Allied Motion motor and the Hurst motors, which other motors are used on turntables or recommended to use substituting my current 10 watts Hurst?
Thanks.
It doesn't sound as if the motor is the problem, unless the problem is vibration. You have an AC synchronous motor, which means the speed is locked to the driving frequency; the Arduino controller is xtal controlled, so very stable. With belt drive tables, belt creep will cause the speed to slowly drift up as the belt and bearing warm up. Belt creep cannot be cured and is not the same as slippage which can be cured with proper tension. If the speed is oscillating, you have other problems that cannot be compensated for with a feedback loop. I would look at the bearing, lubrication, belt contamination, twisting or movement up/down on the platter. If the native stability of the rig is poor, a feedback controller will not be able to correct it. The feedback will correct for long term speed drift.
Hurst motors are notoriously noisy and the 3 phase motor will improve upon vibration and noise, but if the platter does not have good short term stability, a 3 phase motor will not help.
Regards Pyramid.
Thanks for your comments, this one and the many other on threads I have read in this process.
I have verified the aspects you mention as I indicate below, but, will do so again thoroughly.
I know that you have implemented the SG4 control with the Anaheim Automation BLWR172S-24-2000 motor and a specific amplifier for it. Among other solutions, I am considering attempting to implement Stephen’s controller (in 3 phase configuration) with that motor. My Hurst is a 115volts, 10 watts 2 phase motor, to control it I already build a 2 channel amplifier with the TDA7492 amplifier module you have indicated in your posts, so in general to control the 3 phase motor I would add one channel of control and amplification and adjust the voltage down for the motor’s windings.
If I may ask, what are the output specification required to control the motor? I see its a 25 watts 24 volts motor that according to what I understand from your posts is controlled as if it were a 3 phase AC motor.
Anything else I should verify pursuant to the controller’s capacities?
As of the variables you indicated. Have you ever seen one of these Well Tempered “Classic” turntables? Well Tempered Turntables are supposed to be very speed stable and maintenance free. Still, here we are.
The table’s main bearing is a polished steel shaft submerged in a silicone lubricant well and held in place by 5 teflon tips to maintain the main bearing vertical. It is very silent design as there is no ball bearing rumble. I recently verified the lubricant amount in the well and is good.
The motor pulley and platter are made of Delrin, I have cleaned them with alcohol on several occasions in the process.
The table uses a flat neoprene belt that is mounted on the motor pulley with a 180 degree twist, according to William Firebaugh (the designing engineer) that is supposed to “prevent” belt creep. Still, as I have been experimenting a lot lately the belt has stretched (but the motor is free standing and can be mover to compensate the tension). I am waiting for a replacement belt to arrive. I had also tried other, non neoprene belts, from Origin Live and other supplier. They made no improvement to the speed stability and made motor noise transfer through the belt worse.
Regarding the Hurst motor. When you indicate that they are notoriously noisy, do you mean mechanically noisy or electrically noisy?
In these “Classic” Well Tempered tables, the motors are mounted on top of a 12 lb lead base to which they are clamped from the top using a steel plate and 2 screws to the lead base precisely to tame down motor vibrations.
So, maybe the streched belt is causing the problem…
Any ways, again thanks for you comments, I will re assess what you suggest and wait for you response.
Thanks for your comments, this one and the many other on threads I have read in this process.
I have verified the aspects you mention as I indicate below, but, will do so again thoroughly.
I know that you have implemented the SG4 control with the Anaheim Automation BLWR172S-24-2000 motor and a specific amplifier for it. Among other solutions, I am considering attempting to implement Stephen’s controller (in 3 phase configuration) with that motor. My Hurst is a 115volts, 10 watts 2 phase motor, to control it I already build a 2 channel amplifier with the TDA7492 amplifier module you have indicated in your posts, so in general to control the 3 phase motor I would add one channel of control and amplification and adjust the voltage down for the motor’s windings.
If I may ask, what are the output specification required to control the motor? I see its a 25 watts 24 volts motor that according to what I understand from your posts is controlled as if it were a 3 phase AC motor.
Anything else I should verify pursuant to the controller’s capacities?
As of the variables you indicated. Have you ever seen one of these Well Tempered “Classic” turntables? Well Tempered Turntables are supposed to be very speed stable and maintenance free. Still, here we are.
The table’s main bearing is a polished steel shaft submerged in a silicone lubricant well and held in place by 5 teflon tips to maintain the main bearing vertical. It is very silent design as there is no ball bearing rumble. I recently verified the lubricant amount in the well and is good.
The motor pulley and platter are made of Delrin, I have cleaned them with alcohol on several occasions in the process.
The table uses a flat neoprene belt that is mounted on the motor pulley with a 180 degree twist, according to William Firebaugh (the designing engineer) that is supposed to “prevent” belt creep. Still, as I have been experimenting a lot lately the belt has stretched (but the motor is free standing and can be mover to compensate the tension). I am waiting for a replacement belt to arrive. I had also tried other, non neoprene belts, from Origin Live and other supplier. They made no improvement to the speed stability and made motor noise transfer through the belt worse.
Regarding the Hurst motor. When you indicate that they are notoriously noisy, do you mean mechanically noisy or electrically noisy?
In these “Classic” Well Tempered tables, the motors are mounted on top of a 12 lb lead base to which they are clamped from the top using a steel plate and 2 screws to the lead base precisely to tame down motor vibrations.
So, maybe the streched belt is causing the problem…
Any ways, again thanks for you comments, I will re assess what you suggest and wait for you response.
Unfortunately they aren't, but are available second hand. They are almost indestructible, their only weaknesses being that they are inefficient and the lubricant tends to gum up. They are easily disassembled, cleaned, lubed etc.
Some papst outer-rotor motors have their windings optimised for 2 phase operation, some 3 phase. You'll need to verify which before purchase.
There are equivalent outer-rotor motors from the likes of teac, used in their R2R machines.
These hysteresis motors are very much smoother than any 2 phase synchronous motors and also smoother that any shaded pole motors, though the latter, with it's high speed and hence rotational momentum, can work OK.
As for so-called DC motors... brushed DC motors suck when used in a turntable. They drift all over the place, so require complex control mechanisms. They also radiate brush noise. JCarr, whose opinions i take note of, once stated that he successfully used a brushed DC motor at extremely high RPM and geared down, but that it didn't last terribly long. So there is that option to try if anyone is interested.
Brushless DC motors aren't DC motors, they are AC motors with an integrated controller. Some of these motors are superb, but usually the controller is rudimentary at best and certainly not up to being optimised for TT use. Having pulled some of these apart, i'd hazard a guess that they could be successfully re-purposed, without the controller, as AC motors. I'd imagine that they'd work very well, but i've not had time to try it yet.
Hurst motors are mechanically noisy, they can have high vibration from two sources:
1. There is only one bearing at the top of the rotor; the bottom is unsupported and the rotors are not dynamically balanced.
2. The windings float loose between the pole pieces and can vibrate at the line frequency.
I measured various Hurst motors at the link below; the higher the power, the worse they were.
Hurst Motors: 300 RPM vs 600 RPM--Upgrade or Myth?
1. There is only one bearing at the top of the rotor; the bottom is unsupported and the rotors are not dynamically balanced.
2. The windings float loose between the pole pieces and can vibrate at the line frequency.
I measured various Hurst motors at the link below; the higher the power, the worse they were.
Hurst Motors: 300 RPM vs 600 RPM--Upgrade or Myth?
To which i'll add a third, they are poorly made. Compared to a phillips/airpax synchronous motor, the rotor windings are messy, the bushings are soft and wear out quickly and the metal stampings shoddy. IME of course, disassembling a motor from my old AR and comparing it to one used in a Linn.
I have read that thread, very informative.
In the Well Tempered turntable, the motor mount includes a steel ring with a raised center pole. To mount the Hurst motor, the bottom cover must be removed and the bottom of the motor placed on that mount. Due to the center pole of the base, the motor does not have as much play as with the factory back cover.
That along with the clamp helps control the vibration. At least that is the design idea.
Bracing the case will mass load some of the vibration, but it will not eliminate it if the rotor is not balanced.
You mentioned the belt is wrapped about the pulley to eliminate belt creep. Belt creep with an elastic belt can not be eliminated, it is a necessary byproduct of torque. It can be reduced by limiting the amount of torque needed to keep the platter on speed by reducing friction or anything that impedes the platter spinning.
You mentioned the belt is wrapped about the pulley to eliminate belt creep. Belt creep with an elastic belt can not be eliminated, it is a necessary byproduct of torque. It can be reduced by limiting the amount of torque needed to keep the platter on speed by reducing friction or anything that impedes the platter spinning.
I once figured that the outer-router motor from a ReVox or Studer R2R would make a great TT motor. They sure worked well in my tape decks.
I bought a Studer reel motor, which looks very much like the capstan motor. But it sure doesn't sound like it! Thing was so darn noisy I abandoned it quick. I still hold out hope for a capstan motor.
Sure, I get it. The belt is not wrapped on the pulley, its flipped 180 degrees, the belt surface that is in contact with the pulley surface is the opposite to the belt surface that is in contact with platter circumference.
J Gordon Holt of Stereophile did an interview with William Firebaugh about the Well Tempered Turntable design that was published in October 1987. I am sorry to say, I misinterpreted the part about the belt. There he states that he noticed in his experiments that having the belt flipped where it is in contact with the motor pulley has a significant effect on the flutter.Bill Firebaugh: The Well-Tempered Innovator | Stereophile.com
Verifying the details you suggested, last night I noticed that the motor assembly was skewed towards the table spindle. As its heavy and free standing, I moved it and verified the underside. I found that one the three bumpers under the lead base had squished under the weight. So I replaced the three for new heavier ones to level the motor assembly.
Also I received the new belt, so I will verify the operation with the new belt to ascertain if something other than the motor is causing the oscillation.
Again, thanks for all the comments.
Why does the Hurst motors run better with a 1 channel controller and a phase cap?
My experience attempting to get the Hurst PB motor running at more precise 33.333 rpm has been that I get better results using a single phase controller and the motor wired with a phase capacitor, than using a 2 phase controller, and wiring each of the 2 motor windings to its corresponding controller channel, one for 0 degree phase and one for 90 phase.
When running the motor with the 1 channel controller I get more constant startups, speed regulation is not worse than with a 2 phase controller, and can run the motor at 81Hz for electronically controlled 45rpm.
When running the motor with the 2 phase controller I get somewhat jittery startups, similar speed regulation to single phase but with some saturation stops, and can not run the motor at 81Hz for 45 rpm use.
Why is that?
My experience attempting to get the Hurst PB motor running at more precise 33.333 rpm has been that I get better results using a single phase controller and the motor wired with a phase capacitor, than using a 2 phase controller, and wiring each of the 2 motor windings to its corresponding controller channel, one for 0 degree phase and one for 90 phase.
When running the motor with the 1 channel controller I get more constant startups, speed regulation is not worse than with a 2 phase controller, and can run the motor at 81Hz for electronically controlled 45rpm.
When running the motor with the 2 phase controller I get somewhat jittery startups, similar speed regulation to single phase but with some saturation stops, and can not run the motor at 81Hz for 45 rpm use.
Why is that?
I noticed this with some of the Hurst motors as well; I've never been able to find the answer why. I have a half-dozen of the Hurst motors, all different power ratings and series; some of them will run from a 2 phase supply at 81Hz others will not. Some of them have terrible vibration, others not. If one vibrates, a sharp slam against the table top will temporarily stop or reduce the vibration, but not always and it always seems to come back. It is another reason I don't like these motors.