Yes they are it's a two-phase motor but the two coils are probably internally connected to each other , otherwise you can use a two-phase powersupply to get rid of the motorvibration.
Sources for documentation/reading material/restoring/updating Vintage 16" transcription idlers?
- Thread starter MarcelNL
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I'l need to use some kind of powersupply anyway, as this machine has a mechanical speed reduction that is worn and replacements do not exist as far as I know at this point. Speed at 33 rpm is something like 33.6 rpm. The 33 rpm was never designed for records but only for cutting recordings in lacquer plates and playing them back.
Motorvibration is for now the least of my issues ;-)
I managed to get it running pretty silently by polishing the bearing races up to 10.000 grit and using new ball bearing balls
Motorvibration is for now the least of my issues ;-)
I managed to get it running pretty silently by polishing the bearing races up to 10.000 grit and using new ball bearing balls
Yes this mechanical reduction is a problem because it was made specifically that time , I have a Presto 64A were this is done with two motors and gear drive that works fine.
Vibration getting important as soon the arm gets in the picture.
Your welcome we have used the Presto at a hifi demo in Veldhoven years ago amazing sound with NRU tonearm with Ortofon A cartridge.
Yes here the same , inclosed a couple of measurements vibration and speed .
Remarkable speed stability but lot of vibration, I have tuned the phase shift circuit which give a improvement in vibration and cleaner speedspectrum.
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that looks impressive, I wish I knew more about that magic..but will read up...for now stability of speed is not (yet) a great asset of the RCA ... I fear that I need some new bronze bearings for the 33 rpm section and for sure I need to build a speed control as 33,6 is too much.
The only measurement I can do with using an app, and that shows 0.08% wow at 78 rpm (ultra precision main bearing I guess), but 0,2 at 33....but the number is going down with more hours play time.
Not sure if the 'pure sine wave' inverter doing 110V 60Hz is imprecise or the drive train itself, but building a tunable sine wave generator and power amp is on the to do list, after the speaker system...
For now with the tone arm adjusted to the best of my ability it sounds really good already with an old pickering cartridge I've installed to get my feet wet, yet it'll have to compete with the dual Xeon Asus Sage music server.
The only measurement I can do with using an app, and that shows 0.08% wow at 78 rpm (ultra precision main bearing I guess), but 0,2 at 33....but the number is going down with more hours play time.
Not sure if the 'pure sine wave' inverter doing 110V 60Hz is imprecise or the drive train itself, but building a tunable sine wave generator and power amp is on the to do list, after the speaker system...
For now with the tone arm adjusted to the best of my ability it sounds really good already with an old pickering cartridge I've installed to get my feet wet, yet it'll have to compete with the dual Xeon Asus Sage music server.
I’m sure an adjustable sine wave generator and a stereo amp will improve motor’s performance. I recommend you to select a lower voltage than 110VAC for smoother run. Ex. 60-70VAC. As you know voltage is related with torque on AC motors. Additionally I recommend to get rid of phase shifting capacitor and to use a stereo signal with proper phase difference if it’s a two phase motor. In that case you need to build a stereo power amp.
Since the motor has not two separated coils a two phase powersupply is not possible .
Ok. That's why I started my sentence with "if" in my earlier post. An adjustable power supply will also improve a single phase motor.
Tuning the phase cap give probably a bigger improvement as you can see in my vibration measurements at the Presto 64A turntable.
@volken Is there anywhere I can read up on synchroneous motors and fase tuning? So far I found zilch
First measure the voltage at the red_green coil and at yellow-green coil .
For vibration free running these voltages need to be the same ,measurements under load.
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