60 WPC Amplifier for DIY Turntable Motor Drive

I have one comment and two questions.
Comment: be informed that some of arc suppression caps (typically installed parallel to switch, or I tried RC (100R + 0.1uF)) can have a little current go thorough (small current leak) and when your switch is off, your motor will get small current and it will vibrate with no rotation (it is quite audible too).

I have experimented with this on my VPI power switch and what VPI put in doesn't work at my place. The "pop" sound never went away. What I did was I bought a more suitable suppression capacitor (inspired by what was found and used for the PTP Lenco), carefully selecting the capacitance value like 3300 to 3900pF Class X1/Y2 rated. With this type, it worked flawlessly. Yes, there is a very very tiny voltage trickle to the motor but insignificant to cause any harm. The bigger the capacitance, the more voltage trickle to the motor. I used 3300pf and that's that. It stay there.

This is the part: http://my.element14.com/kemet/c927u332myvdba7317/cap-cer-y5v-3300pf-400vac-rad/dp/2440222
 
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Hi Bill,

I'm craving for your vast experience. Please help to me to clarify couple of questions.

a. I do see some gibberish on my SG4 LED display for ½ sec when I turn power ON. Sometimes it is LLLL and sometimes it is other parts of 7 segments.
I think I do see same thing on one of your videos, but not fully sure. Illumination is not that bright and it is happening too fast.
It is normal behave or it is an indication of some issue?
b. Need your advice about voltage setup. What SG4 voltage output would be more appropriate (64 or 128, or somewhere in-between) for Hurst Hurst 3001-001 (3W) and for Premotec 31813 (1.8W, 18mA) morors
running with TDA7293 amp (modded for 13dB gain), and Talema 25VA 12VAC115VAC?
c. Last one. Can I use same model Talema trany to feed TDA7293 amp for these small motors? At the case of 24 Vout needed, it will be 12.5VA. If I can feed 12V to that AMP and it will be sufficient power out, then it
will be 25AV trany. Please let me know. My current toroid is about 150-200 VA min and it is overkill. I hear it is humming for 2-3 sec then I turn power on. It is “loading its core” ……

Thank you.
Alex
 
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a. I do see some gibberish on my SG4 LED display for ½ sec when I turn power ON. Sometimes it is LLLL and sometimes it is other parts of 7 segments.
I think I do see same thing on one of your videos, but not fully sure. Illumination is not that bright and it is happening too fast.
It is normal behave or it is an indication of some issue?

There will be random data on the display during reset (~350mS).


b. Need your advice about voltage setup. What SG4 voltage output would be more appropriate (64 or 128, or somewhere in-between) for Hurst Hurst 3001-001 (3W) and for Premotec 31813 (1.8W, 18mA) morors
running with TDA7293 amp (modded for 13dB gain), and Talema 25VA 12VAC115VAC?

With the SG4 set to 128, you adjust the input pot to the amp so that you have 115VAC out at the motor. The pot is then left at that setting permanently. Set the SG4 attenuator for what ever running voltage you prefer (lower voltage=lower vibration but also lower torque).


c. Last one. Can I use same model Talema trany to feed TDA7293 amp for these small motors? At the case of 24 Vout needed, it will be 12.5VA. If I can feed 12V to that AMP and it will be sufficient power out, then it
will be 25AV trany. Please let me know. My current toroid is about 150-200 VA min and it is overkill. I hear it is humming for 2-3 sec then I turn power on. It is “loading its core” ……

The TDA7293 needs 24VDC minimum (±12VDC to ±50VDC). Pick a voltage that gives you the necessary supply rails for the amp to produce the AC voltage needed to drive the motor directly (24VAC) or to drive the secondary of the step up xfmr (15VAC for a 12V secondary). 15VAC is ~42.5 VPP so you would need a 45VDC supply (±22.5VDC). 24VAC direct to the motor is ~68VPP so you would need a 70VDC supply (±35VDC). The xfmr driving the motor should be rated for 1.25-1.5x the motor power rating. The xfmr powering the TDA7293 should be rated for 4x the motor power rating.
 
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It will quickly be apparent that I don't know much about motors....

I would like to drive the motor on my Empire 208 table using the SG4/TDA7492 setup described in this thread. I have successfully built one to drive a Premotech 110v motor (older Rega).

My question is this: I have heard the Empire motor referred to as a 3 phase motor. Is this a correct understanding? If so, do I need to output 3 signals to the motor instead of 2 like I used for the Premotech motor?

Is there a good place to learn more about the various types of motors?

Thank you for your assistance.
 
I believe DIY member ralphfcooke has done this successfully. I would PM him directly for advice.

You can drive the 3 phase Papst motor with a single phase and the capacitor that came with the table or use a 3 phase drive using the SG4/TDA7492/xfmrs, but it is quite a bit more complex.

There is a good tutorial on motors Here.
 
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I believe DIY member ralphfcooke has done this successfully. I would PM him directly for advice.

You can drive the 3 phase Papst motor with a single phase and the capacitor that came with the table or use a 3 phase drive using the SG4/TDA7492/xfmrs, but it is quite a bit more complex.

There is a good tutorial on motors Here.

Thanks so much for the information. I will contact ralphcooke. I would like to try the more complicated approach as it should be a learning experience.
 
Empire 208 motor

Like member "hirscwi", I'm also attempting the build to use on an Empire 208 Pabst motor. I've finished the SG-4 and using the MK154 amplifier specified for this thread, I'm in process of wiring all the parts together. I'm a novice at this and not particularly confident that I'm knowledgable enough to pull it off w/out blowing it all up!!

I'll post a photo of everything wired up for the group to inspect before I apply power but in the meantime thought I'd post of photo of my Pabst motor to see if it's the same and if there's anything that helps determine the # of phases used.

Please do jump on board "hirscwi", it would be great to have someone else building for the Empire 208 motor.
 

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OK, I found the information in that thread. Still working through the details and am creating a document with the extracted information. I will share that document. I have not reached the point where the SG4 comes into play but that seems straightforward...
 
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OK, here's what I've extracted so far. I'm about 24 pages through the 42 page thread and need to rest my eyes for a while. I do have a question:

The motor on my Empire 208 is wired with a single capacitor (4mfd). I assume this gives only one phase-shifted signal. Does that suggest that the motor is running on only 2 different signals? I assume it would operate on 2 signals but without as much torque and probably more roughly. Is this correct?
 

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Hi,

I realize this is totally off topic but:

I am a machinist who just made a 55 lb. aluminum platter. i made an inverted bearing using a polished tungsten carbide shaft 5/8" diameter with 5/8" radius on top. The bearing bushing is made out of VESPEL ( look it up). Not knowing much about electronics was a problem looking for a motor / controller. Maxon has just came out with the EPOS motor controller along with high precision motors which debuted at the Munich show. Some of these motors have sensors that sample the motor RPM thousands of time per revolution. Matt (VPI owner) is a member of our audio club so getting a drive system is not a problem but I wanted something better. I have some friends researching this project and should know some specifics in a few weeks. Granted, going this way is not exactly cheap but I (and electronic savvy friends) believe the results will be better. I am sure some of you guys are in the same boat as I. Hope this info helps. Good luck.
 
OK, here's what I've extracted so far. I'm about 24 pages through the 42 page thread and need to rest my eyes for a while. I do have a question:

The motor on my Empire 208 is wired with a single capacitor (4mfd). I assume this gives only one phase-shifted signal. Does that suggest that the motor is running on only 2 different signals? I assume it would operate on 2 signals but without as much torque and probably more roughly. Is this correct?

With the phase cap, the motor is running as 3 phase, but not optimally. The 2 direct connections can be looked at as running 0° and 180° since they are out of phase with each other. The lead connected to the cap is ~+90° referenced to the 0° input. So instead of running 0/120/240, it is running 0/90/180. This works, but with higher vibration.
 
Hi,

I realize this is totally off topic but:

I am a machinist who just made a 55 lb. aluminum platter. i made an inverted bearing using a polished tungsten carbide shaft 5/8" diameter with 5/8" radius on top. The bearing bushing is made out of VESPEL ( look it up). Not knowing much about electronics was a problem looking for a motor / controller. Maxon has just came out with the EPOS motor controller along with high precision motors which debuted at the Munich show. Some of these motors have sensors that sample the motor RPM thousands of time per revolution. Matt (VPI owner) is a member of our audio club so getting a drive system is not a problem but I wanted something better. I have some friends researching this project and should know some specifics in a few weeks. Granted, going this way is not exactly cheap but I (and electronic savvy friends) believe the results will be better. I am sure some of you guys are in the same boat as I. Hope this info helps. Good luck.

Do you have a PN for the motor and/or controller?
 
Hi Bill, can I translate your answer to hirscwi for Hurst and Premotec 110-115VAC sync motors when 1 phase with cap vs. 2 phases with 90 deg shift generated has more vibration? I need to consider to mod (to remove cap and run 2 phase) or not on my Wilson Benesch. Any measurement test data can be found somewhere online? Thank you.
 
Hi Bill, can I translate your answer to hirscwi for Hurst and Premotec 110-115VAC sync motors when 1 phase with cap vs. 2 phases with 90 deg shift generated has more vibration? I need to consider to mod (to remove cap and run 2 phase) or not on my Wilson Benesch. Any measurement test data can be found somewhere online? Thank you.

I did some measurements on a Hurst motor here: http://www.diyaudio.com/forums/analogue-source/309925-hurst-motors-300-rpm-vs-600-rpm-upgrade-myth-3.html#post5170383