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Old 6th April 2013, 02:37 AM   #101
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I have a motor question. While using a Portescap 7.5 degree, 24v stepper motor, running it at 81 Hz for 45 RPMs, makes it get very hot. Is it now running outside specs?
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Old 6th April 2013, 09:27 AM   #102
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Quote:
Originally Posted by vdi_nenna View Post
I have a motor question. While using a Portescap 7.5 degree, 24v stepper motor, running it at 81 Hz for 45 RPMs, makes it get very hot. Is it now running outside specs?

Try what I did . Take a speed controllable drill and rotate as best you can to the desired speed ( I used a spectrum analyzer to check Hz ) . Add a load of lets say 1 watt per phase at the suspected output of 14 V rms ( 200 R 1W ) . See what you get on both phases . I suspect that is the maximum voltage when used as a synchronous motor . As a rule of thumb 1/2 DC will be about right .

If you have the inductance of the motor go back to the stepper motor calculator I gave previously in a link . I suspect the ideal stepper rotational max is also very good at AC .

From my tests I would expect 8 to 10 V rms to work well with your motor . 24 V rms AC is about 34 V DC equivalent if a stepper , that would get hot .

A big Crouzet 11W synchronous as I show stripped down gets up to 60 C ( 140 F ? ) at full voltage . Some transformers are rated up to 130 C , a motor is a rotating transformer mostly . The big question then is vibration . the lower voltage will help both vibration and heat .

I hope soon to try a 1.8 stepper . I want 78 RPM . In fact I want 80 for an industrial application .

http://www.daycounter.com/Calculator...lculator.phtml

Last edited by nigel pearson; 6th April 2013 at 09:31 AM. Reason: Add link
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Old 15th July 2013, 07:04 PM   #103
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Hello.

My first post here, and I am already rambling...terribly sorry I posted this in the wrong thread, its not a DIY turntable I have....
I have a Micro Seiki BL-77 turntable, and with no skills as a DIY guy I attempt to understand this thing.
Parts are not easy to come by, I need a dust cover, the finger lift on the headshell is broken and the headshells are impossible to find, and I am looking at the transformer and motor to if things can be improved upon. I will have to buy another BL-77 in order to get parts I think.
Anyway, the motor in this thing is called Matsushita FG Servo Dc 12 volt MHX-5F2R VM but I cannot find any info on this motor. What I find is this, it looks identical, except the the original cannot be easily opened and doesnt have that screw on the side to pull out a pcb.
Matsushita DC Motor 12 V 6000 RPM 39 mm Diameter 12 V Motor Low Current | eBay
From the turntable to the motor there are five cables, amongst them two yellow, and on the e-bay motor there are four terminals, I am just assuming the two yellow cables go together, but I am not sure.
Thought I should try the motor, but I dont dare since I am not convinced where the cables go.
I have a bit of transformer noise, the table is specified to 220volts, we have 230 here but I measure up to 239 at times. I tried a dc filter, by LCAudio, but it didnt help really.
Thinking about getting an enclosure and mount a new toroid transformer, and the power supply board from the turntable in this new enclosure. The power supply board is shown on the picture here with the fuses. Still have to measure the original transformers output voltage before I can get a new one, but I assume its 12 volts since the motor is 12 volts.
Anyone knows if these old DC motors from Micro Seiki is still available, under another name maybe?
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Last edited by MicroSeiki; 15th July 2013 at 07:10 PM.
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Old 15th July 2013, 09:40 PM   #104
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Default Scematic for Micro Seiki BL-77

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Old 20th November 2013, 05:39 PM   #105
gusk1 is offline gusk1  Greece
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Nigel what's your thoughts about this article?

Chang's Vintage Audio & DIY: Turntable Power Supply
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Old 13th December 2013, 04:00 PM   #106
bgruhn is offline bgruhn  United States
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Quote:
Originally Posted by nigel pearson View Post
Try what I did . Take a speed controllable drill and rotate as best you can to the desired speed ( I used a spectrum analyzer to check Hz ) . Add a load of lets say 1 watt per phase at the suspected output of 14 V rms ( 200 R 1W ) . See what you get on both phases . I suspect that is the maximum voltage when used as a synchronous motor . As a rule of thumb 1/2 DC will be about right .

If you have the inductance of the motor go back to the stepper motor calculator I gave previously in a link . I suspect the ideal stepper rotational max is also very good at AC .

From my tests I would expect 8 to 10 V rms to work well with your motor . 24 V rms AC is about 34 V DC equivalent if a stepper , that would get hot .

A big Crouzet 11W synchronous as I show stripped down gets up to 60 C ( 140 F ? ) at full voltage . Some transformers are rated up to 130 C , a motor is a rotating transformer mostly . The big question then is vibration . the lower voltage will help both vibration and heat .

I hope soon to try a 1.8 stepper . I want 78 RPM . In fact I want 80 for an industrial application .

Stepper Motor Calculator
Nigel, Please suggest a value for the phase shift capacitor with this Portescap stepper motor being used as a synchronous AC motor 60Hz.
Thanks in advance,

BillG
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Old 14th December 2013, 12:30 PM   #107
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Hi Bill .

I have just been working with the Linn LP12 for the first time in years . I must say the cheaper motor here seems a better motor if it can be slightly tamed . One massive advantage is that the voltage is low . That means safe to play with and cheap parts . On reflection a much lower voltage is worth trying . The LP12 motor is so puny yet works OK . The torque and vibration can he assessed by ear . You might only need 4 V . This little motor is pretty good if criticizing the typical motor . As a rough guide when the voltage is the same on both phases it is in the right ball park . Start with 10 uF and add some . If you buy some non ( bi ) polar caps these will be fine to get an idea . Perhaps buy a big value film cap later . To be honest the 50 V rated Panasonic's should last for years at this low current .

Here is an example . A few lower values also . You might need 18 uF ( could be a bit more ) . Start with 4 V rms so as to be able to gauge vibration .

ECEA1HN100U - PANASONIC - CAP, ALU ELECT, 10UF, 50V, CAN | Farnell UK
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Old 14th December 2013, 02:27 PM   #108
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Bill give me a link to the motor you intend to use to be sure it's like the one I tried . The rules given before apply . You might need a Variac if wanting fast results . I have done so many turntable motor things recently I could easily get them mixed up .
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Old 14th December 2013, 02:49 PM   #109
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Originally Posted by gusk1 View Post
Nigel what's your thoughts about this article?

Chang's Vintage Audio & DIY: Turntable Power Supply
Sorry I did not answer this before . I suspect it didn't arrive in my in box ? I feel there is one very big error in what he says . RC oscillators are in no way inferior to typical crystal oscillators . The temperature coefficient of a NPO ( COG ) capacitor is 30 ppm . A crystal also . The resistors commonly used often compliment the NPO capacitors and can outclass a crystal . Thus surprising stability and accuracy is arrived at . Adjusted using a strobe needs no 500 frequency meter . A Wien Bridge RC oscillator needs no other filtering in a turntable application . A crystal needs plenty . Also some harmless assumptions he makes are of no importance one way or the other . What matters is phase , voltage and an attempt at reasonable waveform shape . If you want to optimize build a 100 F ( 40 C ) oven around the oscillator . That temperature is unlikely to be exceeded by room temperature . 20 to 25 C suits pickups best . If you have valve amps check this ( or any hot amp ) . 100 F / 40C is not unknown local to the valves . Your pickup will sound less than it's best . Japaneses PU's sometimes were specified 25 C for tropical markets . People in other countries were disappointed with their bargain imports if so , 20 C being more typical here .
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Old 14th December 2013, 03:54 PM   #110
bgruhn is offline bgruhn  United States
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Quote:
Originally Posted by nigel pearson View Post
Hi Bill .

I have just been working with the Linn LP12 for the first time in years . I must say the cheaper motor here seems a better motor if it can be slightly tamed . One massive advantage is that the voltage is low . That means safe to play with and cheap parts . On reflection a much lower voltage is worth trying . The LP12 motor is so puny yet works OK . The torque and vibration can he assessed by ear . You might only need 4 V . This little motor is pretty good if criticizing the typical motor . As a rough guide when the voltage is the same on both phases it is in the right ball park . Start with 10 uF and add some . If you buy some non ( bi ) polar caps these will be fine to get an idea . Perhaps buy a big value film cap later . To be honest the 50 V rated Panasonic's should last for years at this low current .

Here is an example . A few lower values also . You might need 18 uF ( could be a bit more ) . Start with 4 V rms so as to be able to gauge vibration .

ECEA1HN100U - PANASONIC - CAP, ALU ELECT, 10UF, 50V, CAN | Farnell UK
Nigel,

Here is the motor I've ordered, 2 of them. Thanks for your suggestions. Looks like I may get away with an old 6.3VAC filament transformer.

24V STEPPER MOTOR
Portescap #S42L048S02-M5. 24V, 5 Ohm, 7.5 Degree per step. 42mm diameter x 22mm. Two mounting holes on 51mm centers. Four 3" leads. Shaft - 3mm diameter x 11mm long. 16 tooth, 9.75mm diameter ...
Read more
CAT# SMT- At AllElectronics. Should be in next week
$2.50 each

Do you have any idea why a 117 VAC synchronous 300rpm motor from an old BIC TT won't start? On turn on it buzzes but no start running. Give it a manual spin and it runs right on speed and very quiet. Ive tried belt tension and slippage adjustments to no avail. If it would start by itself I could it and be very pleased.
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