Transcriptor HUM

[ShaneF]

Hello!


I recently purchased a transcriptor skeleton turntable. I have a hum problem that -for the life of me- I can't figure out.



With the stylus off the record, it does not hum.



With the stylus on the record, *motor running*, record spinning, it hums.



With the stylus ON the record with the *motor OFF*, it does not hum.


I can not figure this out, for the life of me.



Can you please help?


Thanks,
Shane.

 

[analog_sa]

It is not very clear from your description if when the motor is on the platter is also spinning. Could it be it is not hum but motor rumble? Motor suspension would be the first suspect.

 

[ShaneF]

Yes, the platter is spinning when it hums. It could be motor rumble. Not sure what to do. Any ideas?

 

[ralphfcooke]

Sounds like the motor itself is producing the vibration mechanically, which is being transferred to the platter and hence to the record.
It might sound silly, but first, have you checked for any transit screws?
After that make sure the motor is mounted correctly; have you had a look at the user manual here:- Transcriptors Skeleton - Manual - 2-Speed Universal Turntable - Vinyl Engine
If the motor itself is producing any significant vibration it may be that the phase capacitor is out of spec, not sure what the value should be, but it will be printed on the original part, and after 40+ years may well be due for replacement.
Let us know how you get on, I'm sure other members will come up with other ideas

Good Luck

 

[ShaneF]

That is a potential. I seem to notice the occasional intonation (of instruments) issues. there are no transit screws. I have the manual. No mention of anything.

 

[rayma]

Does this arm have the left and right audio grounds connected together?

 

[ShaneF]

Yes. As I mentioned above... it is NOT electrical.

 

[rayma]

Yes. As I mentioned above... it is NOT electrical.

Take off the belt and turn on the motor. Put on a record. Place the stylus on the record.
Is there hum now?

 

[ShaneF]

this is precisely what I have been saying. With the stylus upon the record, with the motor turned off... there is no hum.

 

[rayma]

this is precisely what I have been saying. With the stylus upon the record, with the motor turned off... there is no hum.

Please read the post #8 again.

 

[ShaneF]

no hum, belt off, stylus on record.

 

[rayma]

no hum, belt off, stylus on record.

With the motor running?

 

[ShaneF]

yes.

 

[rayma]

yes.

Then now you can conclude that it is mechanical.

Next test: If you spin the platter without the belt and play a record, is there no hum then?
If no hum, the motor or belt is the source. If still hum, the bearing.

 

[ShaneF]

I have done that. The bearing is fine. I believe it is the belt but it might also be the phase cap. Getting the value from a source as we speak.

 

[rayma]

I have done that. The bearing is fine. I believe it is the belt but it might also be the phase cap.
Getting the value from a source as we speak.

Then if the capacitor doesn't fix it, replace the belt. You should have a spare anyway.
If the new belt is no help, the motor must have a problem.

 

[ShaneF]

I am thinking it is the motor. I have gone through a couple belts. One was the original which had stretched beyond use. A new one was provided to me which was too tight and the wrong "gauge". So, I cut an inch out of the old belt to get it running and put it back together with an adhesive, but still a hum.

 

[analog_sa]

It looks very much like a motor bearing problem: quiet when idling, but noisy when a lateral force is applied to the bearing. A stiff belt can make this worse.

Is it possible to oil the top of the bearing sleeve?

 

[ShaneF]

I tried a touch of oil. No luck.

 

[Mark Tillotson]

Perhaps wear has given the motor shaft a larger runout? Perhaps the shaft is actually damaged? If you remove the turntable and watch the motor pulley spinning, is it wobbling?