Can you measure the working DC voltage polarity on the capacitor when powered?
I would not change the thermistor unless it is necessary, or unless you understand the operation in detail.
I would not change the thermistor unless it is necessary, or unless you understand the operation in detail.
Unfortunately not, the pcb is sandwiched between the motor (clam-shell) housings so the motor has to be fully dismantled to access it.
I have no reason to change the thermistor so will leave it as is.
I have no reason to change the thermistor so will leave it as is.
We should be able to assume they knew what they were doing with the capacitor polarity.
The + terminal is at near 0V DC, while the - terminal is lower in potential (more negative) by a 7.5V Zener drop.
The + terminal is at near 0V DC, while the - terminal is lower in potential (more negative) by a 7.5V Zener drop.
I think that's a reasonable assumption.
I recall reading somewhere on another forum that an owner had replaced both tantalum caps with Wima MKS caps.
I recall reading somewhere on another forum that an owner had replaced both tantalum caps with Wima MKS caps.
There may not be room. Tantalums are often used where the value and DC voltage would require too large parts otherwise.
The motor is running but the speed does fluctuate a bit - more than I would prefer. I was wondering if either the polarity of the tantalum cap or the thermistor could influence the accuracy/stability of the motor speed.
I would check the mains supply first for fluctuation, after a full mechanical service, cleaning and lubing...the old lube can go dry or lumpy.
And inspect the belt, put a bit of talc on the pulleys to improve grip.
Use a new style lubricant, rated for high temperature and long life.
I tend to use front axle grease, and 20W50 oil...there are also Teflon additive oils and greases available.
And inspect the belt, put a bit of talc on the pulleys to improve grip.
Use a new style lubricant, rated for high temperature and long life.
I tend to use front axle grease, and 20W50 oil...there are also Teflon additive oils and greases available.
I've pretty much done all of that.
The TT is currently powered by a bench power supply, has had a full mechanical service and fitted with a new Oracle belt.
The bearing has been carefully cleaned and lubricated with ISO 100 synthetic oil (containing PTFE). I suspect a higher viscosity oil rather than lower might be better.
The TT is currently powered by a bench power supply, has had a full mechanical service and fitted with a new Oracle belt.
The bearing has been carefully cleaned and lubricated with ISO 100 synthetic oil (containing PTFE). I suspect a higher viscosity oil rather than lower might be better.
Then use a scope or similar instrument to check if the supply to the motor is fluctuating, leaky large caps can cause that.
You can think of mounting the caps elsewhere in the housing and running wires to the PCB holes, if there is room.
That will help you identify and deal with the issue.
Thicker lube acts as a damper, beneficial in some cases, particularly in slow speed mechanisms like turn tables and camera lenses.
You can think of mounting the caps elsewhere in the housing and running wires to the PCB holes, if there is room.
That will help you identify and deal with the issue.
Thicker lube acts as a damper, beneficial in some cases, particularly in slow speed mechanisms like turn tables and camera lenses.
The bench power supply is rock solid. Also, I have replaced the TT on-board voltage regulator and associated transistor and resistors so I am comfortable that this is not where the problem is.
More viscous lubricant does see counter intuitive to me, however, it might be worth a try.
More viscous lubricant does see counter intuitive to me, however, it might be worth a try.
You could also try a thin lube like sewing machine oil while you are at it, think of some way to measure the speed, if you do not have one, a sample rate of 0.05 to 0.1 seconds will be useful.
A phone app, perhaps?
A phone app, perhaps?
All about circuits has a thread on this motor, somebody said use a 555 to drive two transistors in this Hall effect motor.
Another site says these take about 3 minutes to stabilize.
I personally would look at replacing the motor with a BLDC or synchrono motor, if this is a known obsolete part, also known to be a weak performer.
Another site says these take about 3 minutes to stabilize.
I personally would look at replacing the motor with a BLDC or synchrono motor, if this is a known obsolete part, also known to be a weak performer.
This motor is of high quality and was used by many manufacturers worldwide.
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I will have a look at the tantalums tomorrow.
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I will have a look at the tantalums tomorrow.
I would like to try sewing machine oil but the ones I have checked out are mineral oils. Since the bearing contains Teflon I need to use a synthetic oil.
I have read that thread but hope to be able to get a bit more out of this motor before going to that extent.
Thanks, appreciated.
There are Teflon compatible thin synthetic oils, look at clock parts / supplies sellers (for example, Micro-Tools).
Here I tried to find silicon oil for a Swiss surgical motor which runs at 40,000 rpm, and the CNC spindle oil available was thicker than needed, minimum quantity 1 liter...
That is a practical aspect, which is the reason I suggested a clock parts supplier.
Micro-Tools is well known in the camera repair community, I have no ties to them.
Sometimes you have a 'hunting' like in old diesel engines, the speed stabilizes after a few minutes.
To reduce harmonic influences, I would try a 1 MFD/400V and a 400/400V or so nF array in parallel with the mains supply to the table, I assume you are using a mains voltage conditioner.
If the supply is giving lower voltage DC, try it on the mains side, and check the earthing of both the supply and the table, I have seen some unusual effects from the lack of earthing.
Here I tried to find silicon oil for a Swiss surgical motor which runs at 40,000 rpm, and the CNC spindle oil available was thicker than needed, minimum quantity 1 liter...
That is a practical aspect, which is the reason I suggested a clock parts supplier.
Micro-Tools is well known in the camera repair community, I have no ties to them.
Sometimes you have a 'hunting' like in old diesel engines, the speed stabilizes after a few minutes.
To reduce harmonic influences, I would try a 1 MFD/400V and a 400/400V or so nF array in parallel with the mains supply to the table, I assume you are using a mains voltage conditioner.
If the supply is giving lower voltage DC, try it on the mains side, and check the earthing of both the supply and the table, I have seen some unusual effects from the lack of earthing.
I believe light synthetic oils are used on in-line skates so that may be worth a try. Should be readily available.
The owners manual for the Oracle Delphi MkIII has this to say about friction in the main bearing : "Install the platter without the belt and spin it gently. Excessive bearing friction will tend to slow down the platter. Since this can happen to various degrees, one way to determine excessive friction is to watch when the platter comes to a stop, too much friction will force the platter to move backwards slightly."
When I try this test the platter does move backwards slowly indicating excessive friction. I will definitely try a lighter synthetic oil.
The owners manual for the Oracle Delphi MkIII has this to say about friction in the main bearing : "Install the platter without the belt and spin it gently. Excessive bearing friction will tend to slow down the platter. Since this can happen to various degrees, one way to determine excessive friction is to watch when the platter comes to a stop, too much friction will force the platter to move backwards slightly."
When I try this test the platter does move backwards slowly indicating excessive friction. I will definitely try a lighter synthetic oil.
Try 5W20 and 5W30 engine oils, a few drops are all that are needed, synthetics are available, a car garage will give a few drops for free...easier to obtain and use compared to some exotic stuff.
These are common engine oil grades for winter or mixed weather use.
The number in automobile and industrial oil grades tells us the number of seconds a fixed measure of the oil takes to pass through a standard orifice, the instrument looks a bit like an hour glass, more details on line.
A higher figure means a thicker oil, I did feel 100 was too much, but I was not sure to which standard, we get SAE 80W-90, 90, 90W130 and 130 grades in auto gear oils here...220 and 320 grades are found for industrial gear use also.
SAE means Society of Automotive Engineers, API (American Petroleum Institute) standards are also found in the oil business, mostly on the design side.
These are common engine oil grades for winter or mixed weather use.
The number in automobile and industrial oil grades tells us the number of seconds a fixed measure of the oil takes to pass through a standard orifice, the instrument looks a bit like an hour glass, more details on line.
A higher figure means a thicker oil, I did feel 100 was too much, but I was not sure to which standard, we get SAE 80W-90, 90, 90W130 and 130 grades in auto gear oils here...220 and 320 grades are found for industrial gear use also.
SAE means Society of Automotive Engineers, API (American Petroleum Institute) standards are also found in the oil business, mostly on the design side.
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