Bearing wear on an SP 10 mk II PICS

[tubesforever]

I am listing this information for those out there who own or contemplate the purchase of one of these gems. I thought this example might be fun to discuss with the forum.

This is an interesting study. You will see the bearing wear, a previous bandaid fix, and some pics of the motor assembly ou may never have seen before.

If you have questions please feel free to respond.

First off we should discuss the stock SP 10 mk II bearing.

The steel spindle is hardened and polished. It rotates within a bronze side wall bearing that is precision manufactured. The clearances on these bearings is very tight and in years of servicing these I have only had a few that were wasted.

This bearing design puts a button of self repairing plastic at the end of the shaft. This rides on a chrome steel ball that is a light press fit to the bearing shaft. Technics lists these bearings as low friction design.

Interestingly this thrust pad button rotates freely. Think about this a moment. When the friction between the ball and the button is higher than the button against the shaft you will suddenly be listening to a terribly noisy bearing.

With this particular bearing there was contact wear of the ball to the end cap holding the bearing in place. This means the ball which is a light press fit was also spinning against the cap. This indicates that the bearing was exhibiting unnaturally high friction.

I suspect it was run too dry. The lubricant left in the shaft resembled high temperature racing grease but in fact was the debris of the bearing mixed into the Technics oil.

Self repairing plastic has some hard components like glass or zirconium mixed in to help make the material tough. When this gets broken down during wear the material becomes an abrasive.

Notice the wear marks on the side of the bearing spindle shaft. Unfortunately the side wall bearing is also scored.

Picture one shows the bearing shaft and the self repairing plastic button.

The button itself shows about 0.60 thousands of an inch wear or about 1/3 to 1/2 of its usable thickness. However somewhere around 0.40 thousanths of an inch the top hat began to ride on the stator windings. This created enough noiset that the table was repaired before it shorted out the motor.

Picture two shows how someone pressed down the bearing 0.102 inches to get the hat off the motor stators. The overshoot was also an issue but we can discuss that later.

Picture three shows the wear on the stock bearing.

Picture four shows the motor windings. You probably cannot see it but the top of the windings showed transfer from the hat.

Enjoy the photos.

 

[bogle111]

Looking at those pics remind me of those medical "operations" on TV, nasty.

Good pics though. I have an only ever domestic 10 and a second to be done up, which I suspect has had more use. Was this one a radio station one or a domestic one?

Very interesting. Thank you.

 

[marcmorin]

Hi, the bottom pad is simply teflon. Although teflon is credited with being "slippery" it doesn't make for a good thrust material due to its low compression value and non-discript makeup. (no grain structure). The shaft needs refinished to 12 micron crosshatch at 15deg. The spindle bore needs refinished to 12 micron at 60deg crosshatch. That finish dept will hold lubricant in place, and the intersecting angles will produce a 45deg load.

http://www.audiokarma.org/forums/showthread.php?t=405770

There is some information, and application of this in this thread.

 

[tubesforever]

"Hi, the bottom pad is simply teflon. marcmorin"

Marc, I am sure you did not mean to say the thrust pad is pure 100 percent teflon.

The bottom pad is a composite structural plastic with self repairing properties. Back in 1975 I am not sure what blends Technics were looking at. They changed from the SP 10 MKII to the SP 15 models. Then Technics changed again with the SL1200 turntables and other models using the same bearing.

I figure back in the 70's they were using materials such as Teflon, Delrin, glass, ceramics, molybdenum, graphite, and the other usual suspects.

The wear on the shaft indicates that what was blended into the plastic to harden it also scored the hardened steel as it tore apart and circulated in the oil. It takes something pretty hard to do this much shaft wear.

I wonder if we could broadcast here to see if there is a laboratory specialist who is an AK member. I can forward samples of the three thrust pad materials I have to see their composition and percentage. I think gas chromatography would work for this type of testing.

Regardless of the blend, there are better materials out there.

Cheers!

 

[tubesforever]

"Was this one a radio station one or a domestic one? bogle111"

I am not sure of its complete history. By the nature of the wear and its previous bearing press, I suspect this was a radio station turntable sold off and refurbished somewhat. The quick and dirty bearing press solved the hat dragging on the motor windings. The lack of fresh lubrication was disheartening.

There will be new parts on this bearing that will surpass the old technology Technics used back 37 years ago.

 

[marcmorin]

"Hi, the bottom pad is simply teflon. marcmorin"

Marc, I am sure you did not mean to say the thrust pad is pure 100 percent teflon.

The bottom pad is a composite structural plastic with self repairing properties. Back in 1975 I am not sure what blends Technics were looking at. They changed from the SP 10 MKII to the SP 15 models. Then Technics changed again with the SL1200 turntables and other models using the same bearing.

I figure back in the 70's they were using materials such as Teflon, Delrin, glass, ceramics, molybdenum, graphite, and the other usual suspects.

The wear on the shaft indicates that what was blended into the plastic to harden it also scored the hardened steel as it tore apart and circulated in the oil. It takes something pretty hard to do this much shaft wear.

I wonder if we could broadcast here to see if there is a laboratory specialist who is an AK member. I can forward samples of the three thrust pad materials I have to see their composition and percentage. I think gas chromatography would work for this type of testing.

Regardless of the blend, there are better materials out there.

Cheers!

Well, no. Plastic, regardless of what brand name they put on it, as a particle is very abrasive. The usual suspects you mention, Moly would not abrade the metal. Delrin/Teflon mix is known as Delrin AF and "usually" is brown in color.
The "self healing" is simply marketing. The wear on the shaft could be from particulate, and it can be also from simply the oil film shearing under load and the shaft scuffs. That would add particulates to the oil, and would also accelerate thrust pad wear. The thread I listed, and the information on surface structure of both shaft and sleeve is accurate. I've done a bit of bearing design in my lifetime.

 

[Sam Cogley]

There will be new parts on this bearing that will surpass the old technology Technics used back 37 years ago.

I will be interested in hearing about this. My SP-10Mk.II appears to have seen some pretty heavy use.

 

[tubesforever]

The "self healing" is simply marketing. QUOTE]

Mark, I am even more certain you do not mean self-repairing equals self-healing. I totally agree with you that a bearing cannot self heal. Once damage is done then we are dealing with degradated performance from there on out.

For those following the thread, it is important to understand the needs and the complexity of a low rpm, rotational bearing.

Self repairing composite matrix bearing materials allow for damage to the material to occur without resulting in catastrophic failure.

For instance as the ball rotates against the plastic material , components within the substrate will literally tear away. As long as the remaining composite can hold the load while the rotating ball polishes the damaged area then this bearing will survive to see another day.

With the Technics bearings the self repairing quality of the plastic composite allows 24/7 operation of the bearing for decades if properly oiled.

There are some amazing new bearing materials out now for thrust pads and balls. The noise level of LP playback can be significantly lower if we upgrade.

Cheers!

 

[totem]

tubesforever

There are some amazing new bearing materials out now for thrust pads and balls. The noise level of LP playback can be significantly lower if we upgrade.

I am interested to hear what materials you feel provide better wear etc.
There are a bunch of Big direct drive,s of the mid to late 70,s that could
use some attention in the bearing and lube area.

I am soon to do an inspection of a Victor TT-101 as one was previously
found to be lacking in bearing lubrication. We will see what its bearing
and thrust pad looks like.

 

[theophile]

tubes and Mikey Samra posting on AK on the same day:

A mass defection from AA? :scratch2:

This post makes me wonder whether people who haven't liked their SP10II have been listening to one with a defective thrust pad.

It also makes me wonder about the quality of the thrust pad in my GT 2000. The stock platter on the GT 2000 is 6.5 Kg and the optional gunmetal platter was 18.5 Kg (that's not a misprint). I've always considered that since the GT 2000's bearing was designed to cope with the 18.5 Kg platter, with the 6.5 Kg stock platter the bearing would hardly be worn.

I'm not inclined to pull my GT 2000 apart, but if I ever buy another one to re-plinth (which is a dream I have), it'd be interesting to check out the bearing.

Good to see you at AK. Thanks for the post and the photos tubes. :thmbsp:

 

[tubesforever]

tubesforever

I am interested to hear what materials you feel provide better wear etc.
There are a bunch of Big direct drive,s of the mid to late 70,s that could
use some attention in the bearing and lube area.

I am soon to do an inspection of a Victor TT-101 as one was previously
found to be lacking in bearing lubrication. We will see what its bearing
and thrust pad looks like.

I have been using mirror polished hardened metal as a thrust pad for more than 6 years now and it is tougher than nails.

However my new favorite is Sapphire. This particular SP 10 mkII will be getting a brand new spindle. It will be nitrided so it will never wear or scratch in normal use and the table will be set up with a platter plate and mat that will double the rotating mass of the original table.

With the higher mass and lower friction this SP 10 mkII should give the SP 10 mkIII a run for its money.

I have put the Sapphire into my Lenco's, Rek O Kuts, Technics, and a Denon turntable. I can only say that when my used $350 dollar turntable reminds me of a friend's 9.7k dollar turntable I am very pleased with the results.

I can validate that from experiencing it in my own system.

I have a great love of the SP 10 mkII and SP 15 turntables. They are real sleepers if you address the issues that take place with wear and time.

Your table has an equal or superior reputation!

Cheers!

 

[markd51]

Tubes,
Interesting article, and thank you for providing it, and accomodating pics.

I don't own any Technics Tables myself, but such topics highly interest me.

I think I've read in some other articles you either authored, or participated in over on AA, the mention of a vertical "chatter" as one anomaly occuring on such bearings, that have a definite detrimental impact upon playback performance.

And that in another article written some time back by Michael Fremer, about himself hearing micro variations in speed, and a lack of smoothness of playback. I seem to remember that others debated such that Michael commented on as impossible to hear, or even measure, but the question is, was he actually far off base with these claims?

That by nature of design, that there are inherit flaws in virtually all Technics DD Motors due to an inadequate or poor choice of materials and/or design in the Bearing areas? Or maybe a better description of such would be to say "a choice of materials used to meet a price point"?

That fresh out of the box, any/all all Technics Tables have this flawed shortcoming that of course doesn't improve over time?
It seems to make perfetly logical scientific sense, that any Turntable, no matter the design will be influenced upon the sum of parts to be able to then exhibit great performance.

That two major "players" that highly iinfluence Turntable performance will be Tonearm quality, and Drive System quality. That Drive System errors will be a shortcoming that even the world's finest Tonearms will not be able to positively influence, and overcome.

I can see how such improvements can transform a "good" table into a great table. And that many of today's best performing Turnrtables, let's take Galibier Design as one example, seem to have placed much research, time, and money into the quality of their Platters, Platter Bearings, and Drive Systems.

That some vinylphiles I know have made statements in the past about Belt Drive, Tape Drive, Idler Drive, Direct Drive having their advantages, and disadvantages. No doubt a lot of these statements pro and con only hold part truth, and that any such shortcomings may not be attestable to a Belt, Tape, or particular Drive system method, but the quality of the sum of parts are playing a quite important role in performance. Mark

 

[Pio1980]

There is no free lunch in mechanics, concentrated stress always has a penalty.

 

[totem]

Mark
I would have to agree with your above summation, regarding the issue of

hearing micro variations in speed

whether I am able to hear them is not clear but certainly demonstrated
at least visually by the use of the Timeline strobe and how very seemingly
competent TT,s are unable to maintain correct speed.

On the other hand as has been demonstrated some TT,s do.

 

[marcmorin]

Tubes,
Interesting article, and thank you for providing it, and accomodating pics.

I don't own any Technics Tables myself, but such topics highly interest me.

I think I've read in some other articles you either authored, or participated in over on AA, the mention of a vertical "chatter" as one anomaly occuring on such bearings, that have a definite detrimental impact upon playback performance.

Mark

The "vertical chatter" you refer to is caused by failure to terminate energy.
When energy hits a reflective boundary it of course bounces back and forth from boundary to boundary until it natually decays. Unless that original energy
is continuous as would be the case with the drive unit in question.

Which brought BigBill and I into the conversation that spawned this. It eliminates a bottom boundary in a reflective manner into a damping manner.

http://www.audiokarma.org/forums/showthread.php?t=405770

 

[user510]

Hi Tubes.

I see in your photo that you have removed the bottom bearing cap from the motor assembly.

Here's a pic of mine:

I have yet to remove this part. Reason is that while I assume that the cap screws on by machined threads, I can't be certain from the evidence that I have. So my question to you Tubesforever is how did you remove that part without causing any damage? Anyone else have experience removing this part?

-Steve

 

[totem]

Curious myself although I don't see one in my future.
Looks like pot metal or something of that ilk I assume you have tried to rotate it
with no success?
I will go out on a limb and guess it is a press fit.

 

[user510]

Answering my own questions....again

Sorry for the drama. But sometimes this is how I work. Ask the question. Get all worked up about it. Then solve the problem.
A suggestion was made over on diy audio to use a judicious amount of heat to soften the thread sealant within the cap.

This I did using a heat gun. It didn't take a lot of heat.

The strap wrench worked better after the lower motor housing was mounted into the chassis. This improved leverage. Threads proved to be right hand. So with some counter clockwise force the cap smoothly broke free of its position and unscrewed.

By the look of it, there is more to come out of this bearing assembly.

Important details.

-Steve

 

[dmgrant1]

New bearing/spindle for SP10MKIIa

Quote: "I have been using mirror polished hardened metal as a thrust pad for more than 6 years now and it is tougher than nails.

However my new favorite is Sapphire. This particular SP 10 mkII will be getting a brand new spindle. It will be nitrided so it will never wear or scratch in normal use and the table will be set up with a platter plate and mat that will double the rotating mass of the original table.

With the higher mass and lower friction this SP 10 mkII should give the SP 10 mkIII a run for its money."

To Jim: Bought a SP10MKIIa. Have not fired it up yet. How can I determine if the bearing is good or bad? Where does one source the Sapphire bearing? Where do you get a new nitrided spindle?

Thans

 

[totem]

Blue thread sealant not easy to remove as you found out, heat and or
lots of force required to unseat.