Hum from Turntable

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myriad
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#1 erstellt: 12. Okt 2007, 05:19

Hello Guys,
I have a problem.
My tt has started humming recently.
There is a hum:- only when the needle is on the groove and platter rotating.
There is no hum:- when the needle is on the groove and platter stationery.
There is no hum:- when i take off the belt which disengages the motor from the platter and i spin the platter with my fingers.
All this leads me to think that it's the motor which is causing hum.
What do you guys think and what are the remedies to fix this problem?
Thanks

ani
Stammgast

#2 erstellt: 12. Okt 2007, 06:48

Hi,
Can you hear the hum when the turntable is running ie the motor is driving the platter with the arm cued up near the center of the disk ?

If so the cartridge is picking up the stray magnetic field of the motor. From your equip list you must be using Project RPM4 TT and Sumiko Pearl, try using other cartridge with better Magnetic shielding.

Regards
Anil

myriad
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#3 erstellt: 12. Okt 2007, 16:27

ani schrieb:

There is hum only when the arm is in the groove and motor running i.e. the record playing. The hum goes away as soon as motor stops.

ani
Stammgast

#4 erstellt: 12. Okt 2007, 17:27

Is there hum when you cue up the arm with the motor running ?

myriad
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#5 erstellt: 12. Okt 2007, 17:53

ani schrieb:

Is there hum when you cue up the arm with the motor running ?

No

I just disengaged the belt and switched on the motor. I felt lot of vibration coming from the motor. Surprisingly, i did not feel any vibration when i took the motor off from it's rubber suspension when directly placed on the plinth. I put the motor back on suspension, pulling the suspension rubber and tightened the screws. This way the motor got little more elevation than previous thus reducing any chances of touching the plinth. Now there is very minute hum which is tolerable.

ani
Stammgast

#6 erstellt: 13. Okt 2007, 07:02

So it was mechanical noise picked up due to improper motor suspension. Why don't you change the rubber ring used as motor suspension, it might have lost its elasticity due to aging. Similar sized neoprene rubber O-Ring available at shops that sell oil seals and allied rubber products.

myriad
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#7 erstellt: 13. Okt 2007, 13:39

ani schrieb:

Yes I will do so.

Thanks very much Ani