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Post by jukeboxmarty on Feb 4, 2024 18:18:35 GMT
Seeburg used the same value motor capacitors for both 50hz and 60hz models. Speed correction for 50hz was achieved by utilizing a special 50hz gear set. The following posts touch on the concept of changing the motor capacitor's value to achieve a correction of speed, and have been moved here to allow continued discussion... and a possible solution if conventional fixes do not work. Please note that this concept is not mentioned or recommended in any Seeburg documentation and to my knowledge had not been operationally tested. If you are experiencing incorrect turntable speeds on your Seeburg geared for 50hz, I suggest you seek a conventional remedy before experimenting with the following suggestions. |
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Post by dberman51 on May 23, 2024 0:40:13 GMT
The motor capacitor will need to be a larger value for operation on 50 Hz. But does this machine use a transistor motor speed unit? That would be an entirely different story.
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Post by jukeboxmarty on May 23, 2024 1:11:44 GMT
The motor capacitor will need to be a larger value for operation on 50 Hz. But does this machine use a transistor motor speed unit? That would be an entirely different story. No, the motor capacitor is the same as the US 60 Hz version.
And no again... there is no auto speed unit.
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Post by dberman51 on May 26, 2024 2:55:34 GMT
If new capacitors of the original value don't bring the speed up enough, try 1 uF / 2 uF. That's really what it should have to operate on 50 Hz. The idea is to shift the phase of the secondary run winding by 90 degrees at the line frequency, and a lower line frequency requires a larger run capacitor for the same phase shift.
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Post by jukeboxmarty on May 26, 2024 3:27:50 GMT
If new capacitors of the original value don't bring the speed up enough, try 1 uF / 2 uF. That's really what it should have to operate on 50 Hz. The idea is to shift the phase of the secondary run winding by 90 degrees at the line frequency, and a lower line frequency requires a larger run capacitor for the same phase shift. Can you quote some reference?
Overseas Seeburg's were supplied with the same value capacitors as their US counterparts.
The required adjustment in speed is achieved utilizing a 50 hertz gear set. There is no need to alter the value of the capacitor.
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Post by dberman51 on May 27, 2024 21:43:17 GMT
Any text covering split-phase induction motors (which these are) will describe use of a capacitor to create phase shift between the motor's run winding and start winding. The motor may be capacitor-start, in which case the start winding is used only for starting and is disconnected when the motor begins to turn, or capacitor-run, where the capacitor remains in the circuit energizing the start winding continuously to provide more torque. The Bodine motors used in Seeburgs are the latter type. Phase shift is created by capacitive reactance which is proportional to frequency. The equation for capacitive reactance is Xc = 10^6 / (2 * pi * f * C) where Xc is capacitive reactance in ohms, f is frequency in Hertz, and C is capacitance in micro-Farads. The data plate on the motor in my DS-160 specifies a line frequency of 60 Hz and a total run capacitance of 2.4 uF. Ron's book asserts that all the Bodine motors are interchangeable, so this value should apply to them all. The required capacitive reactance is a consequence of the motor winding inductance and resistance, and will be be same regardless of frequency. So it we want to run a 60 Hz motor on 50 Hz we need to increase the size of C to account for the lower f to produce the same Xc. Plugging in the numbers for the Bodine motor, the required total run capacitor value for 50 Hz is 2.4 uF * (60/50) = 2.88 uF. The closest standard value is 3 uF. Why Seeburg didn't change the run capacitor value for 50 Hz operation I do not know. Note that an induction motor will operate at somewhat lower RPM than the line frequency, so changing the capacitor will not increase the speed at 50 Hz to the value at 60 Hz. That's why a change in gearing is needed. en.wikipedia.org/wiki/Induction_motor-David |
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Post by jukeboxmarty on May 28, 2024 2:35:47 GMT
Any text covering split-phase induction motors (which these are) will describe use of a capacitor to create phase shift between the motor's run winding and start winding. The motor may be capacitor-start, in which case the start winding is used only for starting and is disconnected when the motor begins to turn, or capacitor-run, where the capacitor remains in the circuit energizing the start winding continuously to provide more torque. The Bodine motors used in Seeburgs are the latter type. Phase shift is created by capacitive reactance which is proportional to frequency. The equation for capacitive reactance is Xc = 10^6 / (2 * pi * f * C) where Xc is capacitive reactance in ohms, f is frequency in Hertz, and C is capacitance in micro-Farads. The data plate on the motor in my DS-160 specifies a line frequency of 60 Hz and a total run capacitance of 2.4 uF. Ron's book asserts that all the Bodine motors are interchangeable, so this value should apply to them all. The required capacitive reactance is a consequence of the motor winding inductance and resistance, and will be be same regardless of frequency. So it we want to run a 60 Hz motor on 50 Hz we need to increase the size of C to account for the lower f to produce the same Xc. Plugging in the numbers for the Bodine motor, the required total run capacitor value for 50 Hz is 2.4 uF * (60/50) = 2.88 uF. The closest standard value is 3 uF. Why Seeburg didn't change the run capacitor value for 50 Hz operation I do not know. Note that an induction motor will operate at somewhat lower RPM than the line frequency, so changing the capacitor will not increase the speed at 50 Hz to the value at 60 Hz. That's why a change in gearing is needed. en.wikipedia.org/wiki/Induction_motor-David
Seeburg never offered a different motor capacitor for 50hz, and there have been tens of thousands of 50hz Seeburg machines that turn at the proper RPM, without changing the capacitor's value. A capacitor change is not warranted to achieve the correct RPM.
In consideration of this fact, I will be cleaning up this thread shortly.
If you believe that Seeburg made an error when designing and documenting their machines, feel free to start a thread pointing out their error. |
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Post by jukenorman on May 28, 2024 9:39:56 GMT
Hi David,
Any compensation required for the motor capacitor operating at 50Hz, Seeburg probably would have taken care of in the replacement 50Hz gears ratio.
Norman.
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Post by dberman51 on May 28, 2024 15:50:29 GMT
Although your recent post may technically dazzle many readers, changing the capacitor's value is unnecessary.
Seeburg never offered a different motor capacitor for 50hz, and there have been tens of thousands of 50hz Seeburg machines that turn at the proper RPM, without changing the capacitor's value. A capacitor change is not warranted to achieve the correct RPM.
In consideration of this fact, I will be cleaning up this thread shortly.
If you believe that Seeburg made an error when designing and documenting their machines, feel free to start a thread pointing out their error.Not sure how to reply to this. I'm not trying to technically dazzle anybody. In a post on May 25 above, you made an entirely reasonable request for a reference. All I'm trying to do is to provide the logic and reasoning behind my suggestion about the run capacitor when operating at 50 Hz so you can see I'm not just pulling it out of the air. As to whether Seeburg made a design error, I am sure that they consulted with Bodine and decided that increasing the run capacitance would not be necessary. There is some tolerance around the value, and the difference between 2.4 uF and 3 uF is not that great. After all, on the DS and others the motor has to be able to run on 44 Hz! But if the OPs 100-77 uses the same motor as it would in the US, than 2.4 uF is on the hairy edge. I'm sure it worked fine when new, but now 50-60 years later the run capacitor may have lost some if it's capacitance and may now cause slow operation, which after all is why the OP started this thread. So it's entirely possible that that a new run capacitor of the original value will restore the proper speed. However, it may be marginal and all it would take would be a bearing slightly tight, or line voltage just a bit low, and it might run slow. Hence my suggestion. -David |
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Post by dberman51 on May 28, 2024 15:59:08 GMT
Hi David, Any compensation required for the motor capacitor operating at 50Hz, Seeburg probably would have taken care of in the replacement 50Hz gears ratio. Norman. I would have thought so too. That's why I'm surprised that they didn't change the run capacitor, which is usually the only compensation needed. But here are a few questions: Were the UK models designed to operate at 50Hz and 240V, or are they just US models with gearing changed for 50Hz and operating off a transformer? Was it common for US models to find their way across the pond and be modified for 50Hz? And what does the data plate on the OPs 100-77 motor indicate for voltage, frequency and capacitance? That will tell all! -David |
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Post by jukeboxmarty on May 28, 2024 16:19:14 GMT
Not sure how to reply to this. I'm not trying to technically dazzle anybody. In a post on May 25 above, you made an entirely reasonable request for a reference. All I'm trying to do is to provide the logic and reasoning behind my suggestion about the run capacitor when operating at 50 Hz so you can see I'm not just pulling it out of the air. As to whether Seeburg made a design error, I am sure that they consulted with Bodine and decided that increasing the run capacitance would not be necessary. There is some tolerance around the value, and the difference between 2.4 uF and 3 uF is not that great. After all, on the DS and others the motor has to be able to run on 44 Hz! But if the OPs 100-77 uses the same motor as it would in the US, than 2.4 uF is on the hairy edge. I'm sure it worked fine when new, but now 50-60 years later the run capacitor may have lost some if it's capacitance and may now cause slow operation, which after all is why the OP started this thread. So it's entirely possible that that a new run capacitor of the original value will restore the proper speed. However, it may be marginal and all it would take would be a bearing slightly tight, or line voltage just a bit low, and it might run slow. Hence my suggestion.
When I asked for a reference, I was hoping that you would supply Seeburg documentation explaining the need for a capacitor change... not some general phase shift theory. I may also point out that when the mechanism is playing a record, there is only .75mfd or 1.0mfd capacitance in the circuit depending on the model. At the risk of repeating myself.... there is no need to change the value of this capacitor. Even now 50-60 years later, these Seeburg's continue to play at their designed speed. There is no need to suggest to this member (or future members) that a capacitor change is needed. Since this post is kinda hijacked, I will be moving references to changing the value of the motor capacitor (to this thread).
We don't need to make this subject more complex than necessary.
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Post by jukeboxmarty on Jun 1, 2024 1:28:56 GMT
As the above posts were transferred here from another thread, I figured I'd post the outcome here. Another successful repair! (using the Seeburg specified capacitor value). Put in a 0.75uf cap - fixed, now running at the correct RPM. |
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Post by jukenorman on Jun 1, 2024 12:46:36 GMT
I'm reluctant to get overly bogged down in this because it makes me realise that I could have paid more attention to the theory of operation of electric motors during my student days more than half a century ago! But I did plod through the Wikipedia link that David posted and it defied me to find a reference to the phase shift / capacitive reactance relationships that he is quoting above. There is a very good blog on the Bodine website "What is a Synchronous AC Motor?" which for anyone still inquisitive, provides answers and shows that Seeburg knew what they were doing! www.bodine-electric.com/blog/what-is-a-synchronous-ac-motor/Norman. |
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Post by dberman51 on Jun 1, 2024 15:29:34 GMT
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Post by jukenorman on Jun 1, 2024 16:46:38 GMT
Hi David,
I did say I was reluctant to get bogged down in this! The Bodine pdf you referred to states that a Permanent Split Capacitor motor has a speed tolerance of 3% - there is no way that type of motor would be used for record playing purposes with that tolerance! The Seeburg manuals describe the motor as a "split phase capacitor type" so I think it is more likely that the motor Seeburg used is the Reluctance Synchronous Split Phase type which has a stated speed tolerance of "nearly 0%".
I am really in danger of getting out of my depth here so I'll say no more on this - which leaves you to have the final word.
Norman.
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