Platter rotation not smooth - Technics SL 1200 MK2

[Arti]

According to the built-in stroboscope, and the ear, my Technics SL1200 MK2 does not rotate smoothly. There is one platter position when the rotation jerks down for a fraction of a second, and then re-stabilize. One can hear the sound of scratching at the moment when listening close to the Platter. Mostly, it happens once in a full rotation. Consistently.

If I loosen the left screw on the engine plastic covering (below the Platter), rotation is almost stabilized. If I tighten the three screws to the maximum, the condition is so much worse as to be unlistenable.

I bought it about a year ago on ebay. Could it be that the spindle is bent? Or there is a problem with the Platter? The TT is leveled on the shelf.

Would appreciate if someone has a clue.

Thank you.

Vlado

[walpurgis]

Just a thought. Have you taken the platter off and had a look under it to make sure there's not something trapped under it and rubbing, like a bit of paper maybe? Don't take the platter off with the turntable switched on.

[Spectral Morn]

It sounds like the bearing is not seated correctly. Of course the bearing could be damaged or the mounting area under the bearing damaged but I suspect its the first thought. Anyway the easiest thing to try first, though its a wee bit fiddly to do is remove the bearing and put everything back together.

This video shows you how to do this https://www.youtube.com/watch?v=sjhXXDp1-JQ. The video also shows you how to do a basic service/re oil the bearing but that isn't your problem.

This video also addresses your potential problem https://www.youtube.com/watch?v=qLOjUADMNlE




Regards Neil

[Arti]

Platter looks OK, from both sides. Nothing strange.

Vlado

[CageyH]

Disconnect the power, and investigate the bearing.
Make sure that it is sat flat, and there is no dirt underneath it, Also check the bearing for signs of wear/damage.
When reassembling, tighten the screws evenly and check that the platter sits flat with a spirit level.

[Arti]

[QUOTE=Dalek Supreme D L;683930]It sounds like the bearing is not seated correctly...

This video also addresses your potential problem https://www.youtube.com/watch?v=qLOjUADMNlE
------

I did notice the platter is wobbling a bit on the outer edges. Maybe you are right. I'll do it over the weekend and report.

Thanks.

Vlado

[Andrei]

According to the built-in stroboscope, and the ear, my Technics SL1200 MK2 does not rotate smoothly. There is one platter position when the rotation jerks down for a fraction of a second, and then re-stabilize. One can hear the sound of scratching at the moment when listening close to the Platter. Mostly, it happens once in a full rotation. Consistently.

If I loosen the left screw on the engine plastic covering (below the Platter), rotation is almost stabilized. If I tighten the three screws to the maximum, the condition is so much worse as to be unlistenable.

I bought it about a year ago on ebay. Could it be that the spindle is bent? Or there is a problem with the Platter? The TT is leveled on the shelf.

Would appreciate if someone has a clue.

Thank you.

Vlado

"jerks down" in speed or "jerks down" in height?

Try removing the small black plastic cover that sits over the bearing - it is a dust cover but is not really essential.

Post a few pics if you can - this problem looks like it it should be solvable.

[Arti]

"jerks down" in speed or "jerks down" in height?

Try removing the small black plastic cover that sits over the bearing - it is a dust cover but is not really essential.

Post a few pics if you can - this problem looks like it it should be solvable.

It jerks down in speed. I'll try to reassemble the bearings over the weekend, and see if I can make some significant pics.

Many thanks for your time.

Vlado

[walpurgis]

Keep us informed Vlado. We like to see problems sorted out.

[Arti]

Hi again!

So, I took it apart, checked the Bearing, and put everything back very carefully. Result is the same. Still issues with speed. I couldn't find anything wrong with the components.

When I put just the Platter on the bearing itself, holding everything in one hand and then spin the platter by other hand, I hear no noise or scratching sound indicating that the bearing may be OK.

But when I put the platter back on the TT and spin it by hand I can again hear the noise and the scratching sound in regular intervals indicating that there could be a mechanical problem somewhere down the line. It reflects itself in speed fluctuation. The Platter does not look bent. The scratching sound is heard only when you listen close to the Platter.

Everything I checked looked fine. I will try to borrow another platter from a friend next week and see how it works out. After that I am running out of ideas.

A mysterious problem indeed.

Vlado

[RickeyM]

If I loosen the left screw on the engine plastic covering (below the Platter), rotation is almost stabilized. If I tighten the three screws to the maximum, the condition is so much worse as to be unlistenable.

Vlado

Have you tried removing that plastic cover altogether?

[Arti]

Have you tried removing that plastic cover altogether?

Yes. No change.

Vlado

[krugdoktor]

Had a similar problem after changing to a new MN bearing. Turned out to be a small metallic (magnetic) flake that was attracted by the very strong magnet of the motor assembly and got caught between the magnet and the polepieces. After removing it everything was fine.
Imagine my frustration after buying an expensive aftermarket bearing and fitting it to be greeted with a metallic scratching sound and uneven rotation!
Hope this helps!

[Arti]

Had a similar problem after changing to a new MN bearing. Turned out to be a small metallic (magnetic) flake that was attracted by the very strong magnet of the motor assembly and got caught between the magnet and the polepieces. After removing it everything was fine.
Imagine my frustration after buying an expensive aftermarket bearing and fitting it to be greeted with a metallic scratching sound and uneven rotation!
Hope this helps!

I can imagine the frustration. Been there... in my mind.

Can you please explain in more details what exactly happened. Are you referring to the Platter Magnet or the Base motor magnet? Where precisely did you find the flake?

Thanks.

Vlado

[Andrei]

Arti
After you have lifted the platter off you will see a large black disc. After removing that you will see a smaller black plastic disc that sits over the bearing. Remove both of those. Then put the platter back on and have a look/listen. If the sound and speed wobble you have found your problem. Incidentally neither of those black discs in essential. I think they are dust shields.

One other thing I should have mentioned: when you screw down the bearing with the three long black screws, do that with the PCB loose. In theory the screws for the PB and the screws for the bearing should all fit without being forced, but in practice if something is not going to be a 100% fit then it should not be the bearing. So screw the bearing in with all three screws gently at first then 'hand-tight'. Only then tighten the screws to hold the PCB in place.

[Arti]

Arti
After you have lifted the platter off you will see a large black disc. After removing that you will see a smaller black plastic disc that sits over the bearing. Remove both of those. Then put the platter back on and have a look/listen. If the sound and speed wobble you have found your problem. Incidentally neither of those black discs in essential. I think they are dust shields.

One other thing I should have mentioned: when you screw down the bearing with the three long black screws, do that with the PCB loose. In theory the screws for the PB and the screws for the bearing should all fit without being forced, but in practice if something is not going to be a 100% fit then it should not be the bearing. So screw the bearing in with all three screws gently at first then 'hand-tight'. Only then tighten the screws to hold the PCB in place.

Andrei,

Tried what you suggested, but no difference. When both plastic covers removed and the TT turned ON the speed fluctuation was the same as before.

Then I tried your advice to screw down the bearing with the PCB loose. I did notice a slight improvement.

Remember when I said that loosening the left central cover screw improved the stability? I have now put some finger pressure on the spindle in the direction of 3 o'clock while the disc was spinning. The grating sound disappeared and the strobe was stable as long as I applied the pressure. So, I put a small washer under the left bearing hole (a thin paper washer - like brochure type) and fixed all the screws normally. It kind of worked. The stability is not 100% but close enough. I think I'll leave it this way for the time being.

Thanks for your help.

Vlado

[krugdoktor]

I can imagine the frustration. Been there... in my mind.

Can you please explain in more details what exactly happened. Are you referring to the Platter Magnet or the Base motor magnet? Where precisely did you find the flake?

Thanks.

Vlado

Hi Vlado!
I think there is only one big circular magnet which is attached to the underside of the platter. The distance between the inner surface of the ring magnet and the pole pieces (which can be clearly seen after removing the plasic dust cover) is very small and it was here where I found the metallic flake.
The pole pieces are green in the picture and the circular magnet is "imposed" on them.

[CageyH]

Is there any sign of sticking or wear on the bearing when you rotate it by hand? Perhaps you can feel a bit of a notch?
Did you check for dirt on the ball bearing? Has it been oiled recently?

Standard replacement bearings are pretty cheap, so it there is any doubt about the condition, I would replace it.

[Spectral Morn]

Andrei,

Tried what you suggested, but no difference. When both plastic covers removed and the TT turned ON the speed fluctuation was the same as before.

Then I tried your advice to screw down the bearing with the PCB loose. I did notice a slight improvement.

Remember when I said that loosening the left central cover screw improved the stability? I have now put some finger pressure on the spindle in the direction of 3 o'clock while the disc was spinning. The grating sound disappeared and the strobe was stable as long as I applied the pressure. So, I put a small washer under the left bearing hole (a thin paper washer - like brochure type) and fixed all the screws normally. It kind of worked. The stability is not 100% but close enough. I think I'll leave it this way for the time being.

Thanks for your help.

Vlado

Sounds like the bearing isn't sitting straight but is off true. When I suggested the bearing wasn't seated properly it was this as well as maybe not being centred that I was referring to. If the bearing isn't seated right you can get a rubbing sound and the platter rising up and down slightly.

The holes in the turntables base that the bearing is fixed too is pretty poor and easily damaged, never over tighten or you can strip the threads from the holes. It could be that the mounting area is damaged but it's also possible the bearing is damaged.

Is it that the plater is rising and falling at the edge you are seeing, or is it a slowing and increasing in speed. It's not entirely clear to me what's happening.


Regards Neil

[Arti]

Sounds like the bearing isn't sitting straight but is off true. When I suggested the bearing wasn't seated properly it was this as well as maybe not being centred that I was referring to. If the bearing isn't seated right you can get a rubbing sound and the platter rising up and down slightly.

The holes in the turntables base that the bearing is fixed too is pretty poor and easily damaged, never over tighten or you can strip the threads from the holes. It could be that the mounting area is damaged but it's also possible the bearing is damaged.

Is it that the plater is rising and falling at the edge you are seeing, or is it a slowing and increasing in speed. It's not entirely clear to me what's happening.


Regards Neil

Hi Neil,

It was just the speed issue that got me worried. I can see the platter wobbling slightly at the edges, but not very much. Not sure if this is a problem at all.

It looks to me that the Spindle axis is not perfectly vertical when seated as planned. So, when I push the Spindle to the other side by a finger (toward the right side in my case) when the TT is playing, all of a sudden everything works as it should. It is not a gentle push though. The moment I release the push, the strobe start to behave erratically and the grating sound is heard (once in a revolution, followed by strobe irregularities). Theoretically, it could be something else like the hole on the platter that has been mis-drilled or who knows what. Also, the TT base where the bearing is fixed looks all right to the naked eye. It is probably the bearing piece.

Now, I do have some irregularities in speed but it is very contained, more like a blur at regular intervals (once per revolution) but no grating sound that I can hear.

It is not really a final fix, more like a "crutch" but I cannot verify it with another bearing as I do not have one to try. Until then it will have to do.

Hope I have shed some light on the matter.

Kind Regards,

Vlado

[Arti]

Hi Vlado!
I think there is only one big circular magnet which is attached to the underside of the platter. The distance between the inner surface of the ring magnet and the pole pieces (which can be clearly seen after removing the plasic dust cover) is very small and it was here where I found the metallic flake.
The pole pieces are green in the picture and the circular magnet is "imposed" on them.

Thank you kindly for the picture and the explanation.

It seems my problem is another one :scratch:

However, after your post, I did clean the magnet on the platter, just in case.

Thanks again. Much appreciated.

Vlado

[Arti]

Is there any sign of sticking or wear on the bearing when you rotate it by hand? Perhaps you can feel a bit of a notch?
Did you check for dirt on the ball bearing? Has it been oiled recently?

Standard replacement bearings are pretty cheap, so it there is any doubt about the condition, I would replace it.

No, no suspicious signs. It could easily be rotated by hand, even the platter could be rotated on the bearing with no issues. It has been oiled some 6 months ago, but just from the above (only platter removed). I did check for dirt but could not find anything similar, just the grease.

I do agree about replacing the bearings, but would like to be certain that this would solve the matter once and for all. Or, the next thing. Buy it and smile :)

Thanks Kevin.

Vlado

It is all

[Spectral Morn]

Hi Vlado

Thank you for the clarification. Rise and fall can happen if the platter isn't seated right on the spindle, or the bearing isn't, or if it was a DJ deck were the DJ put a lot of pressure on one side of the platter - one of the videos I linked to on youtube earlier was about that - which damages the platter spindle interface.

However what you describe does seem to point to the bearing. Buying a new one isn't that expensive http://www.ebay.co.uk/itm/TECHNICS-SFMZQ20-01-MOTOR-SHAFT-CENTRE-BEARING-SPINDLE-SL1210-SL1200-MK2-MK3-MK5-/301730654121?hash=item46408c67a9 I think that is the only way to suss this problem.



Regards Neil

[Arti]

Yes, so it seems.

Will buy a new one, they are really not expensive.

Thanks for your help.

Vlado

[worrasf]

Yes, so it seems.

Will buy a new one, they are really not expensive.

Thanks for your help.

Vlado

You've probably already checked this but just to say to ensure the PCB is perfectly seated before you tighten down the bearing retaining screws. There is a small hole in 1 corner of the PCB that is for a location lug.
One time I was replacing the bearing I didn't check properly that the lug was through the hole and on tightening the screws it skewed the bearing position ever so slightly and gave me the same problem you describe

[Arti]

You've probably already checked this but just to say to ensure the PCB is perfectly seated before you tighten down the bearing retaining screws. There is a small hole in 1 corner of the PCB that is for a location lug.
One time I was replacing the bearing I didn't check properly that the lug was through the hole and on tightening the screws it skewed the bearing position ever so slightly and gave me the same problem you describe

Hm, didn't know that.

Already ordered the new bearing. This information will certainly come handy.

Thank you.

Vlado

[allthingsanalogue]

There must be either a, something stuck in the coil part of the motor or b, part of the magnet on the underside of the platter bent out of shape.

[Andrei]

Already ordered the new bearing. This information will certainly come handy.

Thank you.

Vlado

This is a good idea, even if the new bearing does not solve the problem. The new bearing will be an improvement because the base of the spindle and the thrustpad will not be worn. (Put a single drop of oil on the thrustpad, and a couple of drops at the top where it can work its way down. You can use a good quality thick engine oil.)

[Arti]

There must be either a, something stuck in the coil part of the motor or b, part of the magnet on the underside of the platter bent out of shape.

Very interesting approach, but I still think the Spindle Bearing is the culprit.

I did check the magnet and the coil part and saw nothing unusual. On the other side, I am not an expert.

I'll know soon enough I guess.

Thank you.

Vlado

[Mike_New]

You may have a slightly warped chassis. it can happen!!!!
Remove the ferrite magnet from the platter. reseat the platter onto the bearing and spin by hand
now listen for any noises or uneven running.
Check by eye that the platter is running true.