VPI HW19 Mk3 Motor speed issue

[gocc]

Hope someone has an idea how to solve this.

I have a VPI HW19 Mk3. US 110V model and I live in Sweden, so it's 220V in the wall. In order to use the player I have a transformer converting 220V to 110V. All good. Speed of 33.3 is fine, stable and correct. But when I move the belt to 45-pulley the platter is turning at 42.5 rpm. So, obviously a pulley problem. But - the pulley is standard, original VPI pulley. And it works fine at 33.3 rpm. Have been in touch with VPI but they ask for the motor speed (300 or 600 rpm) which I do not have a clue about and I really do not want to remove the motor from the plinth just to be able to read the speed marking. (I have a Forsell Air Reference arm mounted and it's NOT simple to set up that arm correctly). Any suggestions?

Thanks!!

 

[Gregadd]

Can they tell from the serial number?

 

[gocc]

Can they tell from the serial number?

That was my first question. Unfortunatelly, no. Which sounds pretty unreasonable.

 

[Gregadd]

You'll have to do some math. The size of the pulley will tell you how fast the motor has to turn to achieve the speed.
They should hard that. Does not sound like they are trying very hard.

 

[gocc]

No, they are not. I asked them to give me both options, one for 300 and one for 600rpm but no answer

 

[Phoenix Engineering]

It's easy to compute: (Pully Dia + T/2)/(Platter Dia + T/2) = 33.333/Motor RPM.
Where T= belt thickness

Rearranging: Motor RPM = 33.333 * (Platter Dia + T/2)/(Pulley Dia + T/2)

The line voltage in Sweden is 50Hz, correct? So the motor speed will be 250 RPM or 500 RPM (RPM=120*Freq/# motor poles and VPI uses Hurst motors with either 12 or 24 poles).

For a 11.5" platter (292mm) and a 0.080" belt (2mm) the pulley should be ~18.5mm for 500 RPM and ~38mm for 250RPM motors.
For a 12" platter (305mm) and a 0.080" belt (2mm) the pulley should be ~19.37mm for 500 RPM and ~39.75mm for 250RPM motors.

As the pulley is stepped for 33/45, if it is correct at 33 it should also be correct at 45. The pulleys are also tapered so moving the belt to a lower groove within the pulley should increase the speed (IIRC, the 250 RPM pulley may not have this option). The problem may lie elsewhere; check for proper belt tension (belt may be stretched out and loose), proper belt diameter, insufficient bearing lubrication or belt slippage (wipe down the pulley, platter edge and belt with isopropyl alcohol).

 

[Gregadd]

Thank you.
Because the gap between the two speeds is so large there is no need to be exact. You may also have trouble finding that info.
Keep us posted.

 

[gocc]

It's easy to compute: (Pully Dia + T/2)/(Platter Dia + T/2) = 33.333/Motor RPM.
Where T= belt thickness

Rearranging: Motor RPM = 33.333 * (Platter Dia + T/2)/(Pulley Dia + T/2)

The line voltage in Sweden is 50Hz, correct? So the motor speed will be 250 RPM or 500 RPM (RPM=120*Freq/# motor poles and VPI uses Hurst motors with either 12 or 24 poles).

For a 11.5" platter (292mm) and a 0.080" belt (2mm) the pulley should be ~18.5mm for 500 RPM and ~38mm for 250RPM motors.
For a 12" platter (305mm) and a 0.080" belt (2mm) the pulley should be ~19.37mm for 500 RPM and ~39.75mm for 250RPM motors.

As the pulley is stepped for 33/45, if it is correct at 33 it should also be correct at 45. The pulleys are also tapered so moving the belt to a lower groove within the pulley should increase the speed (IIRC, the 250 RPM pulley may not have this option). The problem may lie elsewhere; check for proper belt tension (belt may be stretched out and loose), proper belt diameter, insufficient bearing lubrication or belt slippage (wipe down the pulley, platter edge and belt with isopropyl alcohol).

Thank you!

Your calculation is, of course, correct. And it gives me size of the pulley: 18.73(33.333) and 25.64(45). The actual dimensions of the pulley on the player are 18.2(33.3) and 24(45) measured at the bottom of the pulley-groove. So the pulley is off. Way off on 45. Additional measuring of the platter speed (once I realised that even the 33.3 pulley is a bit off) proves the math - the platter is runs at 33.2 which is lower but not so low that it can be heard when playing. But at 45 it's way off. I am guessing that player was sold together with motor speed controller, which would compensate for the size issues of the pulley. Anyway, I will try contacting VPI support again, this time with the motor speed information and hear what they are saying. If I get any answer.

Thanks again!

 

[Gregadd]

Care to share the motor speed with us?

 

[gocc]

Care to share the motor speed with us?

Sure, it's 12-pole motor running at 250rpm in Europe and 300rpm in US.

 

[microstrip]

Thank you!

Your calculation is, of course, correct. And it gives me size of the pulley: 18.73(33.333) and 25.64(45). The actual dimensions of the pulley on the player are 18.2(33.3) and 24(45) measured at the bottom of the pulley-groove. So the pulley is off. Way off on 45. Additional measuring of the platter speed (once I realised that even the 33.3 pulley is a bit off) proves the math - the platter is runs at 33.2 which is lower but not so low that it can be heard when playing. But at 45 it's way off. I am guessing that player was sold together with motor speed controller, which would compensate for the size issues of the pulley. Anyway, I will try contacting VPI support again, this time with the motor speed information and hear what they are saying. If I get any answer.

Thanks again!

You need a new pulley or a motor speed controller. If you are DIY kind of audiophile I can post a recipe to make a cheap high-performance controller.

 

[gocc]

You need a new pulley or a motor speed controller. If you are DIY kind of audiophile I can post a recipe to make a cheap high-performance controller.

Please!! Tried to find similar DIY solutions online but no luck! Another solution might be 3D printed pulley, but a speed controller would be much better - gives flexibility without requiring exact pulley dimensions.

 

[microstrip]

All you need is a free shareware program to create a very low distortion sinusoidal signal - the shown software with a PC sound board is enough, a 50W or more cheap power amplifier and a power transformer 230 / 12V , 230/15V or 230/18V - a common 230/12 V +12V is great if the amplifier has more than 80W. You need a multimeter to measure AC volts.

Connect the output of the soundcard to the input of the power amplifier and the secondary of the transformer to the output of the amplifier - it will work as a step up of, for example 18 to 230V. Power the turntable from the secondary of the transformer. All you have to do is control frequency and amplitude in the generator. Use the AC voltmeter to check voltage at the different points.

Do you want me to add a sketch? I can do it later.

 

[microstrip]

BTW, if you want to open the turntable and drive the motor coils directly it can be dome with just some extra hardware!

 

[gocc]

All you need is a free shareware program to create a very low distortion sinusoidal signal - the shown software with a PC sound board is enough, a 50W or more cheap power amplifier and a power transformer 230 / 12V , 230/15V or 230/18V - a common 230/12 V +12V is great if the amplifier has more than 80W. You need a multimeter to measure AC volts.

Connect the output of the soundcard to the input of the power amplifier and the secondary of the transformer to the output of the amplifier - it will work as a step up of, for example 18 to 230V. Power the turntable from the secondary of the transformer. All you have to do is control frequency and amplitude in the generator. Use the AC voltmeter to check voltage at the different points.

Do you want me to add a sketch? I can do it later.

View attachment 90338

I am sure that this solution might work, but I would not call it simple Will try to either find a speed controller compatible with VPI or 3D print new pulley. But will wait for the (eventual) answer from VPI. Anyway - thanks for the effort publishing this!

 

[microstrip]

I am sure that this solution might work, but I would not call it simple Will try to either find a speed controller compatible with VPI or 3D print new pulley. But will wait for the (eventual) answer from VPI. Anyway - thanks for the effort publishing this!

May be I was not clear, I wanted to keep it short. What part was not simple?
Do you think that a common 3D printer will be precise enough for such task?

 

[gocc]

No, the principle is simple. But in order to make this work you need a computer, an amp and a transformer - a bunch of extra stuff laying around. That's what I thought of when I called the solution for "non-simple" And no, I would not even try to make new pulley with a common, cheap 3D printer. Thinking about making an exact drawing and ordering it from one of all available more or less professional 3D shops available online. The result is matching the drawing 100% and some of the shops offer even a broad selection of materials.

 

[Phoenix Engineering]

Sure, it's 12-pole motor running at 250rpm in Europe and 300rpm in US.

I believe with the dimensions you posted it would be a 12 pole motor running at 500 RPM (600 US)?

Also, I would not measure at the bottom of the groove as the belt will ride somewhere in between the groove bottom and OD of the pulley. The 500 RPM pulley is tapered and the lower grooves will have a larger diameter than the top. Have you tried adjusting the speed by moving the belt lower?

A slightly thicker belt will also increase speed. If the 33 RPM speed is too fast with a thicker belt, try moving the belt to the higher grooves which will be smaller diameter (slower speed).

If you use a speed controller, VPI makes a non-tapered pulley so you can run multiple belts and do not have to worry about the speed changing with belt location on the pulley.

 

[Gregadd]

As a former math tutor always show your work.

 

[gocc]

I believe with the dimensions you posted it would be a 12 pole motor running at 500 RPM (600 US)?

Also, I would not measure at the bottom of the groove as the belt will ride somewhere in between the groove bottom and OD of the pulley. The 500 RPM pulley is tapered and the lower grooves will have a larger diameter than the top. Have you tried adjusting the speed by moving the belt lower?

A slightly thicker belt will also increase speed. If the 33 RPM speed is too fast with a thicker belt, try moving the belt to the higher grooves which will be smaller diameter (slower speed).

If you use a speed controller, VPI makes a non-tapered pulley so you can run multiple belts and do not have to worry about the speed changing with belt location on the pulley.

No, the motor speed is 250/300 rpm. This calculation confirms it:

For a 11.5" platter (292mm) and a 0.080" belt (2mm) the pulley should be ~18.5mm for 500 RPM and ~38mm for 250RPM motors.

Further, pulley on my HW19 is not tapered. There is a single groove on both 33.3 and 45 pulleys. The belt can be positioned only in that single groove, no possibility to move it to shallow or deep part of the groove, there is only single groove.

I have never had a chance to see a HW19 with speed control and do not know if only one pulley is used in such setup.