Vibrations on the tonearm

music box
Post Reply
varunbadola1974
member
member
Posts: 45
Joined: 30 May 2015 13:51

Vibrations on the tonearm

Post by varunbadola1974 » 18 Jul 2019 09:32

Gentlemen,
I have installed a new motor on my Thorens TD 125 MK1 a few days back. It used to start with a shudder initially and changing the speed from 33 to 45 would aggravate the vibration for a while. In due course, the motor has settled down but at times I can feel the vibrations on the tone arm when I place it manually on the record. I have an SME 3012 Series II running on it. It varies from being benign to noticeable. I usually like to attach an active sub in the chain, but have not been able to do that due to this problem. The sub remains quiet till the tonearm is placed on the record and then it starts to growl. The whole problem vanished on its own a few days back but since the last two days it has resurfaced. I have spent almost a year in refurbishing the table and do not have any expertise left to table this problem. Kindly help.
Thanks
Varun

Alec124c41
vinyl engineer
vinyl engineer
Canada
Posts: 22979
Joined: 28 Oct 2002 03:24
Location: North of Toronto, Canada

Re: Vibrations on the tonearm

Post by Alec124c41 » 18 Jul 2019 14:32

I am not personally familiar with how that motor is mounted, but I think it has rubber mounts. If the screws are too tight, it might compress the rubber, negating some of the damping effect.
I think that you are also getting feedback from the speakers. Use your fingers, when this is present, to see what is vibrating. It might be the shelf or the bottom of the turntable. If you find this, you can deal with it more effectively than by guessing.

Cheers,
Alec

varunbadola1974
member
member
Posts: 45
Joined: 30 May 2015 13:51

Re: Vibrations on the tonearm

Post by varunbadola1974 » 18 Jul 2019 17:41

Thanks for the reply. But would I not get feedback thriugh the speakers with the music playing? Even if I pick up the arm on my finger by the headshell holder, I feel the vibration on my finger. 125 does not have rubber mounts. In fact, I took the platter off and inspected the motor by hand and found no vibration there. Could you kindly explain "the bottom of the turntable"? The table is well balanced though. The suspension springs would be my next suspects though. Some part of the sub chassis has to be touching the main chassis to generate this vibration.

Alec124c41
vinyl engineer
vinyl engineer
Canada
Posts: 22979
Joined: 28 Oct 2002 03:24
Location: North of Toronto, Canada

Re: Vibrations on the tonearm

Post by Alec124c41 » 19 Jul 2019 04:43

By "the bottom," I am referring to the underneath side of the box.
Try removing the belt, and resting the stylus on a record, with and without the motor running.

Cheers,
Alec

varunbadola1974
member
member
Posts: 45
Joined: 30 May 2015 13:51

Re: Vibrations on the tonearm

Post by varunbadola1974 » 19 Jul 2019 07:32

I'll try that. Thanks

varunbadola1974
member
member
Posts: 45
Joined: 30 May 2015 13:51

Re: Vibrations on the tonearm

Post by varunbadola1974 » 20 Jul 2019 21:05

Gentlemen,
Nothing was working so I tried pushing my suspended sub chassis to the left as by default my SC is right aligned. The vibrations have minimised though I can still feel some. The subwoofer also growls less now. But it does. Do the springs need to be readjusted? As in, is there a particular way to install them? Could this be the reason? I read in one forum that the shafts next to the cups, if touching the main chassis, could eliminate bass. I think there has to be some part of the sub chassis touching the main one, thus causing the vibrations.
Thanks

Alec124c41
vinyl engineer
vinyl engineer
Canada
Posts: 22979
Joined: 28 Oct 2002 03:24
Location: North of Toronto, Canada

Re: Vibrations on the tonearm

Post by Alec124c41 » 21 Jul 2019 23:40

I had a top end JVC turntable. With the motor off, and stylus on the record. there was bass feedback, when turned up. The box was acting like a drum, and the only thing that stopped it was to put a slab of foam underneath, sandwiched between the shelf and the bottom, not interfering with the feet that kept it level.
I also put a solid slab, in this case 30mm mdf, on the shelf, with an elastic pad between them, to stop vibrations from the shelf.
Fingertips can be sensitive enough to feel vibrations in the shelf, or surfaces of the plinth, as well as the arm.
Moving the sub was a good start.

Cheers.
Alec

jcidave1
senior member
senior member
United States of America
Posts: 251
Joined: 17 Mar 2013 14:42
Location: SE Virginia

Re: Vibrations on the tonearm

Post by jcidave1 » 22 Jul 2019 11:44

I am sorting a new to me SME 3009 series II on a TD 125 MK1. I took some time to adjust the 3 spring suspension adjusters to make certain that the floating assembly truly does float and not touch any other part of the machine. I could wiggle the test table it was sitting on and it played perfectly without skipping. I would also make sure the machine is sitting level wherever it is.
How tightly have you mounted the arm to the armboard? Just for a test, I would loosen the 4 arm mounting screws to make sure the 4 rubber grommets are not compressed in any way. Make it loose and see what that does.
You could also try to remove the bottom board of the plinth but put the 4 feet back on. See what that does.

varunbadola1974
member
member
Posts: 45
Joined: 30 May 2015 13:51

Re: Vibrations on the tonearm

Post by varunbadola1974 » 22 Jul 2019 18:00

I took a few pictures of the PCB from my phone, which apparently are too large to be attached. But I can make out that the Film caps are bloated. Filter caps and others were changed recently so they look fine. I think I'll recap the complete board. Can the small resistors be left as it is? A friend suggested that I take off every thing and give the board a benzene or a white petrol wash. it seems that the last owner did not clean the board properly before installing the new caps.

Post Reply