Cutting vibrations from a (Garrard) synchronous motor.
I am using a idler drive TT witch I improved in many ways like the central spindle bearing to make it more silent and create a black background. With an idler drive you always have the problem that the idlerwheel and therefore the motor makes a direct contact with the platter. If the motor vibrates, and the synchronous motor from my old Garrard does, so the vibrations is detectable, hearable.
I was therefore in the process of replacing my synchronous motor with a more silent DC motor. But I remembered me an article about reducing the voltage on a AC-motor to reduce vibrations. After research I discovered that might help. Loricraft-Garrard does it with the 301-401-501 types and I understand Linn does it with some types of powersupply (high voltage to start the platter and on speed cutting the voltage). So I thought to give it a try.
I took a simple small light dimmer, cheap version €12,- suitable for halogen as well. And placed it between the mains of the turntable. By turning the wheel from the dimmer at more than 15 degr. the motor stopped with some noise so maximum cutting of voltage is only about 10 degr. I measured the voltage is was 202 Volt. Then I used my stethoscope (ideal for detecting vibrations, even a toy version works!) and noticed indeed a reduction of about a third of the vibration noise. I tried it several times, about third was cut.
But now the strange thing; with my stethoscope I heard a reducing of about a third of the vibration noise but after listening records the rumble was reduced far more, at least 2/3 and almost not hearable any more. Strange.
I was very exited of this improvement and therefore like to share this with you. Probable the trick is well known but I could not find it so easy on this forum.
Note: the Garrard I am using is old, from the time that the voltage in the Netherlands was 220V now the voltage in almost whole Europe is 230V so this is maybe the reason in my case it works fine.
I am using a idler drive TT witch I improved in many ways like the central spindle bearing to make it more silent and create a black background. With an idler drive you always have the problem that the idlerwheel and therefore the motor makes a direct contact with the platter. If the motor vibrates, and the synchronous motor from my old Garrard does, so the vibrations is detectable, hearable.
I was therefore in the process of replacing my synchronous motor with a more silent DC motor. But I remembered me an article about reducing the voltage on a AC-motor to reduce vibrations. After research I discovered that might help. Loricraft-Garrard does it with the 301-401-501 types and I understand Linn does it with some types of powersupply (high voltage to start the platter and on speed cutting the voltage). So I thought to give it a try.
I took a simple small light dimmer, cheap version €12,- suitable for halogen as well. And placed it between the mains of the turntable. By turning the wheel from the dimmer at more than 15 degr. the motor stopped with some noise so maximum cutting of voltage is only about 10 degr. I measured the voltage is was 202 Volt. Then I used my stethoscope (ideal for detecting vibrations, even a toy version works!) and noticed indeed a reduction of about a third of the vibration noise. I tried it several times, about third was cut.
But now the strange thing; with my stethoscope I heard a reducing of about a third of the vibration noise but after listening records the rumble was reduced far more, at least 2/3 and almost not hearable any more. Strange.
I was very exited of this improvement and therefore like to share this with you. Probable the trick is well known but I could not find it so easy on this forum.
Note: the Garrard I am using is old, from the time that the voltage in the Netherlands was 220V now the voltage in almost whole Europe is 230V so this is maybe the reason in my case it works fine.
Attachments
Triumph, considerusing a Variac..
basically an adjustable AC voltage transformer. They are quiet and will allow a finer adjustment of the Voltage.
"Dimmers" (at least here in N.A.) are terrible anywhere near an audio system. The potentiometers are usually not very good and "rattle" at lower voltage.
The fact that reducing the motor noise by approx 1/3 results in an overall reduction in noise of approximately 2/3 suggests that the turntable has other issues (probably mechanical) and that the motor noise has a profound on these other mechanical bits.
stew
basically an adjustable AC voltage transformer. They are quiet and will allow a finer adjustment of the Voltage.
"Dimmers" (at least here in N.A.) are terrible anywhere near an audio system. The potentiometers are usually not very good and "rattle" at lower voltage.
The fact that reducing the motor noise by approx 1/3 results in an overall reduction in noise of approximately 2/3 suggests that the turntable has other issues (probably mechanical) and that the motor noise has a profound on these other mechanical bits.
stew
Hi,
Thyristor / Triac (simple light dimmer) control of a synchronous motor
is not a good idea. (unless its an electric drill .... not synchronous)
A simple voltage dropping resistor is a far better idea. A variac
even better with its noise filtering but far, far, more expensive.
Perhaps the motor needs a service and possibly new mounting rubber.
🙂/sreten.
Thyristor / Triac (simple light dimmer) control of a synchronous motor
is not a good idea. (unless its an electric drill .... not synchronous)
A simple voltage dropping resistor is a far better idea. A variac
even better with its noise filtering but far, far, more expensive.
Perhaps the motor needs a service and possibly new mounting rubber.
🙂/sreten.
First, I'm a little confused, but I am not familiar with Gerrard turntables either. It was my understanding that the Thorens TD124 Idler drive still has a belt between the idler drive wheel and motor. This would imply to me that there is no more of a direct connection of the motor to the platter than a belt drive. I didn't think the motor was directly connected to the idler wheel in any way, just through a belt.
As for motor reduction, most people find that a reduction of motor noise has a pretty profound effect on rumble noise and thus background noise. I wont try and quantify it, but I to have felt its as big if not bigger than many other changes we make such as cartridge or tonearm.
The best way, as I understand it, to reduce motor noise is to ensure that a perfect sinwave is sent to the motor, and that the phase shifted wave is equally as perfect, including a perfect shift. Most turntables, yours included, use a capacitor to cause this shift. Capacitors aren't perfect for this, not only is the shift not perfect, but variations in the caps value can create variations in the degree of the shift. You may want to check that and make sure it checks to factory spec. Additionally, some have suggested that, with an oscilloscope, you could try different cap values until you get the right amount of phase shift.
An even better way is to actively synthesize the 60 hz or 50hz sine wave and the shifted sine wave, so that it can be adjusted more precisely. Such devices aren't so cheap to impliment, nor that easy, but is is basically what Thorens, Rega, Linn etc all do to minimize noise. The reduction in voltage helps, but is not as profound as ensuring the right phase shift.
As for motor reduction, most people find that a reduction of motor noise has a pretty profound effect on rumble noise and thus background noise. I wont try and quantify it, but I to have felt its as big if not bigger than many other changes we make such as cartridge or tonearm.
The best way, as I understand it, to reduce motor noise is to ensure that a perfect sinwave is sent to the motor, and that the phase shifted wave is equally as perfect, including a perfect shift. Most turntables, yours included, use a capacitor to cause this shift. Capacitors aren't perfect for this, not only is the shift not perfect, but variations in the caps value can create variations in the degree of the shift. You may want to check that and make sure it checks to factory spec. Additionally, some have suggested that, with an oscilloscope, you could try different cap values until you get the right amount of phase shift.
An even better way is to actively synthesize the 60 hz or 50hz sine wave and the shifted sine wave, so that it can be adjusted more precisely. Such devices aren't so cheap to impliment, nor that easy, but is is basically what Thorens, Rega, Linn etc all do to minimize noise. The reduction in voltage helps, but is not as profound as ensuring the right phase shift.
Garrards and Thorens and idler drives...
idlers by definition use a wheel that is in contact with a motor shaft, and with the platter.
AFAIK (and I own a few), the Garrards use this, Thorens and Lenco (as well as Bogen, Rek-o-cut, etc). pjpoes : I think you may be confusing idler wheel turntables with flywheel style, such as some of the VPI models that use a belt between the motor and a flywheel, and the flywheel and platter.
As I previously stated (and sreten reinforced this), a variac is the best way to go, but usually quite expensive.
Triumph, the end result is what we are all after. But do check the condition of the idler wheel (including bearings), the motor mounts (often rubber and most likely aged hardened), and the motor operation itself.
I've toyed with the idea of making a new, from scratch, idler wheel turntable. The need of course is for a robust and quiet motor, good bearings for the idler wheel itself, and some sort of soft material for the friction surface of the idler wheels. And a platter, main bearing, voltage controller, etc....
stew
idlers by definition use a wheel that is in contact with a motor shaft, and with the platter.
AFAIK (and I own a few), the Garrards use this, Thorens and Lenco (as well as Bogen, Rek-o-cut, etc). pjpoes : I think you may be confusing idler wheel turntables with flywheel style, such as some of the VPI models that use a belt between the motor and a flywheel, and the flywheel and platter.
As I previously stated (and sreten reinforced this), a variac is the best way to go, but usually quite expensive.
Triumph, the end result is what we are all after. But do check the condition of the idler wheel (including bearings), the motor mounts (often rubber and most likely aged hardened), and the motor operation itself.
I've toyed with the idea of making a new, from scratch, idler wheel turntable. The need of course is for a robust and quiet motor, good bearings for the idler wheel itself, and some sort of soft material for the friction surface of the idler wheels. And a platter, main bearing, voltage controller, etc....
stew
Hi,
Some synchronous motors are shaded pole, direct mains power, no capacitors or resistors.
🙂/sreten.
Some synchronous motors are shaded pole, direct mains power, no capacitors or resistors.
🙂/sreten.
Hi,
Sreten wrote:
Maybe not so good idea but…..it works just fine with my Garrard.
Sreten wrote:
Because of this great success I am searching for a variac. Don’t mind of spending a few €, I know it works.
Sreten wrote:
The motor is just fine. I checked the bearings and mounting rubber. I service this machine myself.
It is the voltage!
Sreten wrote:
There is no belt.
pjpoes wrote:
The change I made on the arm and spindle bearing had a greater effect but that was because both were of very worse quality. But indeed a silent background has a great effect on the sound tough. I am very pleased with this improvement.
pjpoes wrote:
Indeed my Garrard has no capacitor or resistor.
IT WORKS!!! Both detectable with my stethoscope as well with a record. And I am not surprised when it works with more synchronous motors. Tune the voltage with a stethoscope, there is a certain minimum vibration when you change the voltage. In my case it was 202Volt. Lower and it start to vibrate again, until it stops with a lot of vibration.
On this site you can read this:
Once I was satisfied with the arm and cartridge, I plugged the Garrard into a $40 variac that I had purchased off e-bay. Like many turntable motors, the Garrard motor runs with less vibration at less than maximum voltage. My mains voltage is 117v. With the variac, I found that I could drop the voltage to 104v without losing speed. Below 104v, the speed drop could be compensated for by adjusting the eddy brake. Below 92v, the sound quality disappeared. With a little experimentation, I found that 100-102v seemed to give the best sonics.
But again the voltage in Europe is now 230V it use to be 220V.
Sreten wrote:
Maybe not so good idea but…..it works just fine with my Garrard.
Sreten wrote:
Because of this great success I am searching for a variac. Don’t mind of spending a few €, I know it works.
Sreten wrote:
The motor is just fine. I checked the bearings and mounting rubber. I service this machine myself.
It is the voltage!
Sreten wrote:
There is no belt.
pjpoes wrote:
The change I made on the arm and spindle bearing had a greater effect but that was because both were of very worse quality. But indeed a silent background has a great effect on the sound tough. I am very pleased with this improvement.
pjpoes wrote:
Indeed my Garrard has no capacitor or resistor.
IT WORKS!!! Both detectable with my stethoscope as well with a record. And I am not surprised when it works with more synchronous motors. Tune the voltage with a stethoscope, there is a certain minimum vibration when you change the voltage. In my case it was 202Volt. Lower and it start to vibrate again, until it stops with a lot of vibration.
On this site you can read this:
Once I was satisfied with the arm and cartridge, I plugged the Garrard into a $40 variac that I had purchased off e-bay. Like many turntable motors, the Garrard motor runs with less vibration at less than maximum voltage. My mains voltage is 117v. With the variac, I found that I could drop the voltage to 104v without losing speed. Below 104v, the speed drop could be compensated for by adjusting the eddy brake. Below 92v, the sound quality disappeared. With a little experimentation, I found that 100-102v seemed to give the best sonics.
But again the voltage in Europe is now 230V it use to be 220V.
Ah well, like I said, I don't know Gerrard tables, just Thorens. The Thorens uses a belt by the way. I don't know if they ever made an idler wheel with no belt.
Thorens TD124 Description
The TD124 that I am familiar with has only used a belt attached to the idler wheel though. This was true in both the version I and II. You can see the description in the link I sent. It would be incorrect to say that all idler drives imply a direct connection to the motor, but apparently, as is the case with this Garrard, its true of some.
Is the motor in the garrard similar to that used in the old empire grease tables? Well ok, the cap issue wouldn't matter anymore if they don't use a cap for phase shift, and I don't know how these motors work, but I would assume that a synthesized 60hz sinewave would still be better than direct out of the wall in reducing noise. I would even think a decent T filter would improve things.
Thorens TD124 Description
The TD124 that I am familiar with has only used a belt attached to the idler wheel though. This was true in both the version I and II. You can see the description in the link I sent. It would be incorrect to say that all idler drives imply a direct connection to the motor, but apparently, as is the case with this Garrard, its true of some.
Is the motor in the garrard similar to that used in the old empire grease tables? Well ok, the cap issue wouldn't matter anymore if they don't use a cap for phase shift, and I don't know how these motors work, but I would assume that a synthesized 60hz sinewave would still be better than direct out of the wall in reducing noise. I would even think a decent T filter would improve things.
The Thorens ...
really should not be classified as an idler drive then. It would be safest to qualify it a a hybrid.
In this case it seems that it hardly matters (TD124). As I haven't looked at the guts of one , I assumed that if described as an idler,it was. The Garrards I am familiar with use different drives, one with idler (the Lab 80), and one with belt (the Z100 SB).
Regardless, the motors can be silenced as described. And as long as the bearings for all the wheels are good (on the Thorens) then everything else that holds true for the Garrards should hold true for the Thorens, regarding the basic table.
stew
really should not be classified as an idler drive then. It would be safest to qualify it a a hybrid.
In this case it seems that it hardly matters (TD124). As I haven't looked at the guts of one , I assumed that if described as an idler,it was. The Garrards I am familiar with use different drives, one with idler (the Lab 80), and one with belt (the Z100 SB).
Regardless, the motors can be silenced as described. And as long as the bearings for all the wheels are good (on the Thorens) then everything else that holds true for the Garrards should hold true for the Thorens, regarding the basic table.
stew
yes yes, I am not actually trying to reduce the vibrations on mine. I agree that a variac is a good idea, I was just suggesting that improving the signal is important too, if not more important. A resynthesized 60hz AC signal made a bigger difference on my turntables than anything else I tried. Not that a lower voltage didn't also help immensely, but the quality of the AC is very very important.
pjpoes..., clean AC...
cannot be over stated. This is often the missing link that so many strive for, but do nothing about.
Obviously as a turntable/arm/cart/phono-stage is a complete system, both electrical and mechanical, it makes absolute sense to do what can be done to improve all possible parameters. Also please note, that I was not trying to be critical. Sometimes I come across that way and that is not my intent.
stew
cannot be over stated. This is often the missing link that so many strive for, but do nothing about.
Obviously as a turntable/arm/cart/phono-stage is a complete system, both electrical and mechanical, it makes absolute sense to do what can be done to improve all possible parameters. Also please note, that I was not trying to be critical. Sometimes I come across that way and that is not my intent.
stew
This isn't an issue for this guy or this problem, but my main turntable is a customized design using parts from an Acoustic Solid unit I bought. The bearing is very nice, the motor housing well constructed, even the AC sync motor is very good. The problems I have are motor vibration caused by phase issues with the 3 phase motor. I tried a resynced supply, but no luck, it needs fine tuning of the phase shift. I haven't opened the motor housing yet, but I will either vary the caps value to vary the phase shift, or if I feel adventurous actually build a 3 phase supply and adjust the phase shift that way. Next issue is how to dampen a solid stainless steel platter which has no dampening materials at all, without unbalancing it. My thought is that the dampening properties of the mat on top help, but my measurements with the accelerometer suggests it had minimal effect. Solution two is to drill and tap holes in a precise ring around the table and insert brass or aluminum hex head set screws (my assumption being that different metals have different resonances and the better dampened brass will help tame the steel). Solution three is to stick a piece of dampening materials on the bottom, but with no machined recess, it would be potentially visible.
Anyway, I mention this because I imagine these same issues are true of all tables. I know that a common mod on Thorens tables is adding dampening to the underside of the player. Constrained layers is a good design idea, but not really applicable after the fact. I have a technics SP15 that was given to me (hand me down/over) that I have used to compare. I don't love the sound, but I know a lot of people argue that the speed accuracy, wow & flutter, etc was at its pinnacle with some of the best designs from Technics and others during the 80's. Again, not my cup-o-tea, but its a good measurement reference. Currently the Wow and Flutter is near the limits of my measurements for both of those players, with the modified acoustic solid maybe edging the technics out depending on frequency. I can measure down to .003% accurately and they both are at around .006-.01 (again, depending on frequency, time of day, weather, moon phase, room, magic rocks, etc). Also, if you look at a spectral analysis of the two players with test tones, I think the belt drive units I have tested all look better than the direct drives, and I do wonder if that is the real reason so many think they sound better. The Tone is presented with much greater leptokurtic shape (its a stats term for curve shape, I don't know the right term to use). Unless I'm confused on how these devices should work, it seems like a 1khz tone should contain the 1khz tone, not a 1.01, 1.02, 1.03,...1.3khz, etc. Yeah it should contain that fundamental plus the harmonics as that is the reality, but those frequencies about the fundamental should not be reproduced, and are simply a result of system reproduction problems. I've noticed that every improvement I make the turntable with regard to reduction of vibrations and ringing have brought about further improvements in the leptokurtic shape of the test tones. The one big exception was when I replaced the plinth with a plywood plinth instead of the acrylic plinth, it made things worse, in every way, but I think sounded better, plus it looks better. The difference was very slight, so who knows.
Anyway, I mention this because I imagine these same issues are true of all tables. I know that a common mod on Thorens tables is adding dampening to the underside of the player. Constrained layers is a good design idea, but not really applicable after the fact. I have a technics SP15 that was given to me (hand me down/over) that I have used to compare. I don't love the sound, but I know a lot of people argue that the speed accuracy, wow & flutter, etc was at its pinnacle with some of the best designs from Technics and others during the 80's. Again, not my cup-o-tea, but its a good measurement reference. Currently the Wow and Flutter is near the limits of my measurements for both of those players, with the modified acoustic solid maybe edging the technics out depending on frequency. I can measure down to .003% accurately and they both are at around .006-.01 (again, depending on frequency, time of day, weather, moon phase, room, magic rocks, etc). Also, if you look at a spectral analysis of the two players with test tones, I think the belt drive units I have tested all look better than the direct drives, and I do wonder if that is the real reason so many think they sound better. The Tone is presented with much greater leptokurtic shape (its a stats term for curve shape, I don't know the right term to use). Unless I'm confused on how these devices should work, it seems like a 1khz tone should contain the 1khz tone, not a 1.01, 1.02, 1.03,...1.3khz, etc. Yeah it should contain that fundamental plus the harmonics as that is the reality, but those frequencies about the fundamental should not be reproduced, and are simply a result of system reproduction problems. I've noticed that every improvement I make the turntable with regard to reduction of vibrations and ringing have brought about further improvements in the leptokurtic shape of the test tones. The one big exception was when I replaced the plinth with a plywood plinth instead of the acrylic plinth, it made things worse, in every way, but I think sounded better, plus it looks better. The difference was very slight, so who knows.
pjpoes, your turntable "sounds" very interesting....
--you can certainly tell what modality dominates my learning style...
The Technics, and almost all direct drives like mass. The old Garrards do as well. If I make the leap, I'd suggest that whether coupled directly to a motor or via an idler wheel, all directly coupled types (idler and DD), would seem to benefit from this. There is even a massive rebuild of a Sugden BD2 (belt drive) that completely defies "common sense" but is apparently very good (but 100# s + ! )
As far as platter dampening, you might try what Oracle did years ago...a large rubber "belt" on the outside of the platter (on the edge). As I am not sure of your technical background (please do not misconstrue this as an insult), I provide this as an example:
Ask your mechanic why they wrap large black rubber "elastics" around a brake drum or rotor when they machine them. It turns out that besides reducing the amplitude of the horrendous noise produced, if they are not wrapped you run the risk of setting up standing waves and creating cracks in them. Unless equipped to accurately (dynamically) balance a platter, I'd try the elastic band thing first. Surgical tubing may work or the black rubber often used in heavy duty "bungee" cords. Usually only a few dollars anywhere tarps are sold.please look here:Oracle photos
As far as your motor noise goes, definitely you are on the right track. Any pictures of your table?
Triumph, If you can get a variac at a reasonable price, I would certainly try that. You could also, as sreten suggests, use a simple resistor to drop the voltage as needed. Is this an old Garrard Z100 SB? The Garrards have great motors...The Z100, a uses the same "Lab" series of motors as the Lab80, etc...
stew
--you can certainly tell what modality dominates my learning style...
The Technics, and almost all direct drives like mass. The old Garrards do as well. If I make the leap, I'd suggest that whether coupled directly to a motor or via an idler wheel, all directly coupled types (idler and DD), would seem to benefit from this. There is even a massive rebuild of a Sugden BD2 (belt drive) that completely defies "common sense" but is apparently very good (but 100# s + ! )
As far as platter dampening, you might try what Oracle did years ago...a large rubber "belt" on the outside of the platter (on the edge). As I am not sure of your technical background (please do not misconstrue this as an insult), I provide this as an example:
Ask your mechanic why they wrap large black rubber "elastics" around a brake drum or rotor when they machine them. It turns out that besides reducing the amplitude of the horrendous noise produced, if they are not wrapped you run the risk of setting up standing waves and creating cracks in them. Unless equipped to accurately (dynamically) balance a platter, I'd try the elastic band thing first. Surgical tubing may work or the black rubber often used in heavy duty "bungee" cords. Usually only a few dollars anywhere tarps are sold.please look here:Oracle photos
As far as your motor noise goes, definitely you are on the right track. Any pictures of your table?
Triumph, If you can get a variac at a reasonable price, I would certainly try that. You could also, as sreten suggests, use a simple resistor to drop the voltage as needed. Is this an old Garrard Z100 SB? The Garrards have great motors...The Z100, a uses the same "Lab" series of motors as the Lab80, etc...
stew
Pjpoes
Nice word ‘leptokurtic’, wikipedia explains it nicely, I know now what you mean.
About the platter damping of a one inch thick solid stainless platter, personally I wouldn’t worry about it. Steel thick like that is no comparing with my 3mm thick aluminum platter which rings like a bell. I dampened it with some self-sticking anti-vibration plates used in car doors.
About the vibrations from your Acoustic solid synchronous motor. The trick with the dimmer worked for me because I think the following reasons:
- It is a more old type of synchronous motor good and I reckon not so good as a modern synchronous Acoustic Solid motor.
- My synchronous motor has no resistor or cap. I don’t know if this trick works with cap types.
- It is just a voltage tuning no fase, but I really don’t know what a Triac lightdimmer does with the fase.
- The motor was designed for 220V now the voltage is 230V.
Nanook I am going to try a Variac but again a lightdimmer does the trick already and I can’t hear any negative effects on the sound report result in a few weeks. Until now it is just a reduction of rumble there is no effect on the bass, tremble or soundstage.
A simple T-filter doesn’t do this trick. I experienced with several T-filters (also a recommendation of TNT-audio) but it doesn’t work at all. Some of them create electric hum. My experience, it is a waste of all effort to try this, and I wasted some time on this. The power is good enough for a synchronous motor as it comes out of my wall. It is the VOLTAGE!
Problem is it is almost impossible to adjust the voltage to the point of the minimum of vibration just by listening to (test)records. You have to measure it (with a bearing checker )or simply hear it with…
Nice word ‘leptokurtic’, wikipedia explains it nicely, I know now what you mean.
About the platter damping of a one inch thick solid stainless platter, personally I wouldn’t worry about it. Steel thick like that is no comparing with my 3mm thick aluminum platter which rings like a bell. I dampened it with some self-sticking anti-vibration plates used in car doors.
About the vibrations from your Acoustic solid synchronous motor. The trick with the dimmer worked for me because I think the following reasons:
- It is a more old type of synchronous motor good and I reckon not so good as a modern synchronous Acoustic Solid motor.
- My synchronous motor has no resistor or cap. I don’t know if this trick works with cap types.
- It is just a voltage tuning no fase, but I really don’t know what a Triac lightdimmer does with the fase.
- The motor was designed for 220V now the voltage is 230V.
Nanook I am going to try a Variac but again a lightdimmer does the trick already and I can’t hear any negative effects on the sound report result in a few weeks. Until now it is just a reduction of rumble there is no effect on the bass, tremble or soundstage.
A simple T-filter doesn’t do this trick. I experienced with several T-filters (also a recommendation of TNT-audio) but it doesn’t work at all. Some of them create electric hum. My experience, it is a waste of all effort to try this, and I wasted some time on this. The power is good enough for a synchronous motor as it comes out of my wall. It is the VOLTAGE!
Problem is it is almost impossible to adjust the voltage to the point of the minimum of vibration just by listening to (test)records. You have to measure it (with a bearing checker )or simply hear it with…
Attachments
Hmmm.........
There seems to be NIHS with using a series resistor.
FWIW you cannot measure the voltage produced
by a dimmer accurately as it is not a sine wave.
I suspect if you actually knew what a light dimmer does to
voltage and current, you would be convinced it is terrible.
🙂/sreten.
Simplistically a diac/triac dimmer progressively removes
(sets to zero) sections of an AC waveform cycle.
The dimmer the setting the wider the set to zero section.
There seems to be NIHS with using a series resistor.
FWIW you cannot measure the voltage produced
by a dimmer accurately as it is not a sine wave.
I suspect if you actually knew what a light dimmer does to
voltage and current, you would be convinced it is terrible.
🙂/sreten.
Simplistically a diac/triac dimmer progressively removes
(sets to zero) sections of an AC waveform cycle.
The dimmer the setting the wider the set to zero section.
Sreten, NIHS? Sorry couldn’t find this in Wikipedia, do not know this abbreviation.
If you mean why not using a resistor. Of course this can be done but which value? I want to adjust, with the triac it is rather precise, so a I think a variac is a better idea.
A Triac sets sections of the AC waveform to zero, but it works with me, maybe that is the trick and a variac won’t work? Hoping to get a variac in a few weeks let you know then.
If you mean why not using a resistor. Of course this can be done but which value? I want to adjust, with the triac it is rather precise, so a I think a variac is a better idea.
A Triac sets sections of the AC waveform to zero, but it works with me, maybe that is the trick and a variac won’t work? Hoping to get a variac in a few weeks let you know then.
Hi,
Not invented here syndrome.
A simple dimmer does not "tune the voltage with no phase".
All you need to do is ascertain the operating current of the motor
and then the drop of an additional series resistor is fairly trivial.
You only need say 3 values, e.g. 1K, 2.2.K, 4.7K.
By wiring in series you can make 1K, 2.2K, 3.2K, 4.7K, 5.7K, 6.9K, 7.9K.
One assumes you find the value where the motor stalls and then
reduce it somewhat for consistent operation. As far as I know
the lowest voltage operation requires a bit of manual help
for starting, or a 3 position OFF/START/ON switch.
🙂/sreten.
Not invented here syndrome.
A simple dimmer does not "tune the voltage with no phase".
All you need to do is ascertain the operating current of the motor
and then the drop of an additional series resistor is fairly trivial.
You only need say 3 values, e.g. 1K, 2.2.K, 4.7K.
By wiring in series you can make 1K, 2.2K, 3.2K, 4.7K, 5.7K, 6.9K, 7.9K.
One assumes you find the value where the motor stalls and then
reduce it somewhat for consistent operation. As far as I know
the lowest voltage operation requires a bit of manual help
for starting, or a 3 position OFF/START/ON switch.
🙂/sreten.
http://www.alliedelec.com/Search/Pr...9700285&SEARCH=9700285&DESC=RWM06226801JA15E1
Hi,
3W resistors should be plenty high enough.
If the strobe light is a bulb it does matter where you the resistor.
Just go for the most convenient point.
Which for testing might be the fuse position of the mains plug.
🙂/sreten.
Hi,
3W resistors should be plenty high enough.
If the strobe light is a bulb it does matter where you the resistor.
Just go for the most convenient point.
Which for testing might be the fuse position of the mains plug.
🙂/sreten.
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