Bearing Maintenance

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xczar
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Bearing Maintenance

Post by xczar » 18 Dec 2013 20:28

Anyone using a few drips of oil or grease on their main bearings?

Been reading that one should, and should not do this. Any experience here on your 30 year old Denon`s?

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Re: Bearing Maintenance

Post by Dimal » 19 Dec 2013 13:16

G'day "xczar"... :)

A lot of Denon TTs from this era don't readily lend themselves to regular lubrication of the motor bearings, as the motor is a completely unitary component and not designed for this. Rather, you would have to remove the motor ass'y and then disassemble it in order to gain access to the bearings, and since it requires this much disassembly, one might as well completely clean and then replace the bearings' oil - depending on the model.

If you are concerned with the state of the bearings/lubrication in your TT, then perhaps a complete removal and overhaul needs to be planned...

Mal.

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Re: Bearing Maintenance

Post by EdAInWestOC » 19 Dec 2013 15:59

I can only speak based on the experiance I have with the structure of the motor in my Denon DP-62L.

The same type of motor is in the DP-72L, DP-75 and DP-80. The motor in the DP-62L has a metal plate over the top of the motor held in place by four screws. You can remove the motor from the plinth by removing four screws that hold the motor in place. On the DP-62L the motor is plugged into the main PCB by a molex type plug.

Once the motor is removed you can remove the four screws that hold on the top metal plate I wrote about above. Once that metal plate is removed you can grab the spindle and pull upwards to remove the spindle assembly from the motor housing. This can be difficult to remove because the spindle fits snugly into the motor housing and there is some resistance to removing the spindle. Just keep upwards force on the spindle and turn it until air finds its way into the spindle hole and the spindle works free.

Be careful because there is a ball on the bottom of the spindle assembly that rests between the spindle and the thrust pad at the bottom of the hole where the spindle is inserted.

Once the spindle and ball is removed and carefully set aside you need long cotton swabs to reach inside the motor housing all the way down to the thrust pad. You have to clean out the old dirt and whatever else resides down there before adding any new oil.

You can also examine the thrust pad for any wear. In the case of my DP-62L, there should be no wear on the thrust pad if its in good shape. The ball rests between the end of the spindle and the thrust pad. It should be spinning on a smooth surface (which is the thrust pad). If there is any indentation you have a main bearing issue and it will become audible...if its not already.

The end of the spindle has an indentation where the ball rests. This should be polished and free of any defects. If this indentation has any signs of wear you also have a main bearing issue.

If both the thrust pad and the end of the spindle look like they are in good shape you need to clean the spindle opening so that no foreign matter is left in the hole. Once your cleaning is done you can a use few drops of any medium weight synthetic oil in the bearing. Make sure that the ball is lubricated before you reassemble the motor.

Invert the spindle and place the ball on the end of the spindle. While holding the spindle inverted place the motor over the spindle and work the spindle into the motor opening until the spindle is fully inserted. Once this is done you can turn the motor right side up and put the metal plate back on the motor.

The type of motor assembly above is not unique to Denon and you may find this type of motor in other manufacturer's turntables. Just be careful when you remove the spindle out of the motor and be aware of the ball that should be on the end of the spindle assembly.

Note that the spindle assembly I describe above is the same spindle that protrudes above the turntable platter and is where you place a LP's center hole onto.

Ed

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Re: Bearing Maintenance

Post by xczar » 19 Dec 2013 22:02

Dimal wrote:G'day "xczar"... :)

A lot of Denon TTs from this era don't readily lend themselves to regular lubrication of the motor bearings, as the motor is a completely unitary component and not designed for this. Rather, you would have to remove the motor ass'y and then disassemble it in order to gain access to the bearings, and since it requires this much disassembly, one might as well completely clean and then replace the bearings' oil - depending on the model.

If you are concerned with the state of the bearings/lubrication in your TT, then perhaps a complete removal and overhaul needs to be planned...

Mal.
Hello Dimal, ........... I have no noticeable issues with the bearings. The spindle spins smooth and solid. I was thinking out loud that a drop or two of oil would make it down the perimeter of the spindle possibly?
I guess most Denon owner`s not experiencing any issues just leave it alone?
I`m just hoping the age of the oil/grease in there is still ok.

Merry Christmas

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Re: Bearing Maintenance

Post by xczar » 19 Dec 2013 22:08

EdAInWestOC wrote:I can only speak based on the experiance I have with the structure of the motor in my Denon DP-62L. ...................
Ed
Hi Ed, ........... Reading your experience with the 62L seems like it is not too tough a job. Lifting the platter on my 40F, it seems that removing a few screws, I can get in there. But I don`t want take a chance of screwing things up in there, if it`s not necessary.

Great your able to do these type of overhaul`s.

Merry Christmas

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Re: Bearing Maintenance

Post by Dimal » 20 Dec 2013 08:17

xczar wrote:I was thinking out loud that a drop or two of oil would make it down the perimeter of the spindle possibly?
Not recommended mate. Probably only end up where oil shouldn't be located and then you've got a hell of a clean-up job on your hands... :(

Merry Xmas to you too, :D
Mal.

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Re: Bearing Maintenance

Post by EdAInWestOC » 20 Dec 2013 18:56

xczar wrote:
EdAInWestOC wrote:I can only speak based on the experiance I have with the structure of the motor in my Denon DP-62L. ...................
Ed
Hi Ed, ........... Reading your experience with the 62L seems like it is not too tough a job. Lifting the platter on my 40F, it seems that removing a few screws, I can get in there. But I don`t want take a chance of screwing things up in there, if it`s not necessary.

Great your able to do these type of overhaul`s.

Merry Christmas
xczar,
As long as you look out for the ball bearing when you remove the spindle assembly from the motor housing you should be OK. Denon as well as other manufacturers advertised their turntables as "lifetime" bearings. Unfortunately thats a fairly loose term and when a Denon table gets over 25 years old the main bearing should be inspected. At the very least it should be cleaned out and relubed.

Once you get the hang of the maintenance its not too tough. I am fairly mechanical by nature so I use "not too tough" phrase with a bit of a disclaimer.

Denon DD motors are usually 3 piece assemblies...the spindle assembly, the ball bearing itself and the motor housing with the thrust pad at the bottom of the well. I took very good care of my DP-62L but the main bearing had to be replaced all the same.

My DP-62L now sports a jeweled and ceramic bearing. The original bearing started making a regular thump noise at 33 RPM and it turned out to be a worn thrust pad, ball bearing and the spindle shaft needed machining.

I had the bearing redone by Applied Fidelity and am very happy with their work. The jewel/ceramic bearing is very quiet and the low level resolution of the table is as good as you can find on that model Denon.

Ed

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Re: Bearing Maintenance

Post by xczar » 23 Dec 2013 20:23

Ed, ..... I wish I could see a cross section of what is in my Denon. I would feel better about working on it if I knew what to expect what`s in there. Do any of these cross sections look anything like your 62L? Seems like a single ball bearing design that the spindle assembly lays on?

https://i105.photobucket.com/albums/m21 ... ypes-1.jpg

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Re: Bearing Maintenance

Post by EdAInWestOC » 24 Dec 2013 12:55

xczar wrote:Ed, ..... I wish I could see a cross section of what is in my Denon. I would feel better about working on it if I knew what to expect what`s in there. Do any of these cross sections look anything like your 62L? Seems like a single ball bearing design that the spindle assembly lays on?

https://i105.photobucket.com/albums/m21 ... ypes-1.jpg
xczar,
Here is a photo of my motor and main bearing posted by the person who did the work at Applied Fidelity:

http://usr.audioasylum.com/images/3/334 ... _00121.jpg

If you look at the photo closely you can see the spindle assembly on the right, the new ceramic ball bearing just below the spindle assembly, the motor housing at the center of the photo and the motor itself on the left.

Its a little hard to see but the spindle that protrudes through the platter and the place where you put your records onto is at the right hand side of the spindle assembly. The spindle assembly is resting on the tip of the spindle and the edge of the "bell housing". The brass tinted bell type housing that is part of the spindle assembly goes over the motor and spins between the motor and the motor housing.

If you look at the left hand side of the spindle assembly and at the left hand end of the spindle itself, you can see the other end of the spindle and the place where a machined "dish" is manufactured so that the ball stays put between the spindle and the thrust pad. You cannot see the jewel thrust pad in this photo because it was not yet put into the motor assembly yet.

If I get this correct, it was placed at the bottom center of the motor housing. You can see the place where the old thrust pad was with the indentation and three holes around that indentation on the bottom center of the motor housing.

The person who does this work spends a lot of time with very informed people to evaluate and test various bearing materials. The jewel/ceramic bearing that was put into my motor was tested under load for an extended period of time before being offered to the public.

This same person also did extended tests on the audibility of worn main bearings and its much more audible than one would believe. A few years ago I received a CDR with test cuts from different bearing materials in a Technics SL-1200...IIRC. The first test cut was with the worn stock bearing and comparing that track to subsequent tracks with new bearings using different materials made the point.

Worn out bearings in these old turntables is not an ideal situation and maintenance on, or replacment of the main bearing, is more needed than some would like to think.

Let me know if this helps,
Ed

PS: I cannot see the photo you posted because I am typing this at work and many photos and almost all videos are blocked here.

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Re: Bearing Maintenance

Post by xczar » 26 Dec 2013 17:19

Yes, thank Ed, this helps a lot.

- So, as I suspected, the 'Main Bearing' is simply a single, small ball bearing that is between the bottom of the spindle, and the top of the thrust pad?

- Interesting how this is engineered. Do you know how the motor is fixed to the housing? Screws to/thru the thrust pad?

- Do you know the exact condition of your old bearing? Was it visibly worn? Or gauged with calipers to tell it was worn?

- Was this entire assembly accessed from the top of the table, under the platter? Now I wonder if mine is similar?

- Were you experiencing any symptoms prior to the new bearing? Can I ask what kind of cost the job was?

Nice job on the repair. Wish I could have seen it done. Thanks again for the image.

Serge

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Re: Bearing Maintenance

Post by EdAInWestOC » 27 Dec 2013 17:26

xczar wrote:Yes, thank Ed, this helps a lot.

- So, as I suspected, the 'Main Bearing' is simply a single, small ball bearing that is between the bottom of the spindle, and the top of the thrust pad?

- Interesting how this is engineered. Do you know how the motor is fixed to the housing? Screws to/thru the thrust pad?

- Do you know the exact condition of your old bearing? Was it visibly worn? Or gauged with calipers to tell it was worn?

- Was this entire assembly accessed from the top of the table, under the platter? Now I wonder if mine is similar?

- Were you experiencing any symptoms prior to the new bearing? Can I ask what kind of cost the job was?

Nice job on the repair. Wish I could have seen it done. Thanks again for the image.

Serge
xczar,
Yes, I believe it was the three small screw holes at the bottom of the housing that held the motor in place but I am relying on memory here (big disclaimer). The person who redid my bearing had to modify the bottom center of the motor housing to mount the jeweled thrust pad that was slightly different in size compared to the stock thrust pad.

And yes, a main bearing is as simple as a ball sitting between the end of the spindle and riding on a thrust pad. Not much to write home about but the materials chosen for these elements have an effect of the table's sound. Also remember that the side of the spindle only has oil to keep it from grinding against the hole it sits in. All of these things have to be perfectly machined, within tolerance and have oil to keep them spinning nicely.

I participated in the evaluation of bearing materials when http://www.appliedfidelity.com/ first started doing main bearings. The different materials have a slight effect on the table's sound and to prove the point Applied Fidelity created a CDR where a sound track was recorded using a Technics SL-1200 with a stock bearing (which was a bit worn). The main bearing was replaced with three different combinations (IIRC) of ball and thrust pad materials and the same track was re-recorded. I believe I still have that CDR sitting on a shelf and the stock vs the three improved bearings are indeed different. Some of the comparisons are slightly different but the most superior bearing materials were chosen buy a group of people who received the CDR. I believe the people who compared the bearings came to similar decisions. Not everyone chose the same "best" bearing (perhaps due to CD playback differences) but it was clear that better bearing materials yield a quieter main bearing and better playback.

My old bearing had a slight "dimple" on the thrust pad. The thrust pad is supposed to be absolutely flat without any wear. Any sign of a "dimple" being worn into the thrust pad indicates that the main bearing is starting to wear out.

The main bearing will accelerate its wear. Its not a linear thing. As the "dimple" grows in depth the friction increases and the wear increases likewise. The main bearing starts to take on the characteristics of a drill instead of a bearing.

On the bottom of the spindle its the same. The small "cup" machined on the bottom of the spindle is supposed to keep the ball in place. Unfortunately, if it starts to wear that "cup" will become distorted and some sort of audible effects start to show up.

Its dependant on the individual table's main bearing and the state of the wear. On my DP-62L there was an audible "thump" each revolution at 33RPM but there was no sound at 45RPM. That "thump" started to show itself through the speakers as the wear progressed so I had to do something about the main bearing.

It was odd as hell. When I sat and listened to a LP I heard this very low level "thump", "thump", "thump" and couldn't figure out where the dammed thing was coming from. I tried turning off the ceiling fan and a bunch of other things until I listened through the plinth. Crap.

My DP-62L is now a much better table that is capable of increased low level detail retrieval. The change was not dramatic. The "thump" is gone and the table reproduces the background and quiet sounds with a spooky authority. If someone is looking for more gut wrenching bass they need to look somewhere else.

Many old tables have main bearing problems and the audibility varies depending on the specific bearing design and how the individual bearing is worn. Technics bearings have a plastic part that is designed to wear gracefully. Thats a nice approach but the plastic bits that are worn away have to go somewhere. Sometimes the plastic bits find their way between the side of the spindle and the hole it sits in. And you have noise again.

I guess the moral of the story is that all things wear out. A turntable that is well taken care of will still wear out eventually. My DP-62L was very well taken care of but I still had to recap the electronics and replace the main bearing before it ran like new again.

A new bearing is not cheap. The parts themself are not too expensive. Its the detailed machining that costs money. If you just replace the ball and thrust pad you might get away with it. If the bottom of the spindle is starting to wear you will likely wear out the new ball and thrust pad much sooner than expected.

Main bearing replacement requires that all of the surfaces are polished like a mirror and nothing is worn unevenly. This type of micro maching takes the proper equipment and experience to yield a good main bearing. In my DP-62L's case the spindle's "cup" was worn and needed machining to restore its shape.

Once that was done the difference in length of the spindle (now slightly different due to the machining) caused an increased gap to be accounted for. The thrust pad was mounted higher to compensate for the machining of the spindle.

All of this stuff is best handled by people who understand main bearing requirements.

Good luck with you table,
Ed

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Re: Bearing Maintenance

Post by xczar » 30 Dec 2013 18:57

Good information Ed,

I would have thought that the thrust pad was cupped similar to the spindle? If it is flat, it seems the bearing would receive more pressure at it`s apex.

After reading this posts a couple of times and reading about your symptoms of a worn bearing, I got to thinking. Has anyone put a stethoscope to their table? Much should be heard from one. So I went down in my basement and dug out a stethoscope I have for listening to motors, I use for cars and motorcycles. This thing is pretty damn sharp. Picks up the slightest sounds. This type of stethoscope has a thin, solid, metal rod for holing against a subject, as opposed to a big round pad that a doctor would hold up to your chest.

When listening to my Denon, placing the rod around the platter while it`s running, I can only hear the slightest sound of the motor running. A pretty consistent, smooth sound. No thumping, jarring, or anything that might suggest a worn bearing component. It was good to hear.

But, I am still interested in getting a look in there and give everything a good cleaning and inspection. Sure wish I knew someone that has accessed this model. I don`t want to start randomly pulling screws from below the platter, without knowing what I`m loosening.

I am assuming your bearing was accessed from the top of the table?

Happy New Year. ..... Serge

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Re: Bearing Maintenance

Post by EdAInWestOC » 31 Dec 2013 12:38

xczar wrote:Good information Ed,

I would have thought that the thrust pad was cupped similar to the spindle? If it is flat, it seems the bearing would receive more pressure at it`s apex.

After reading this posts a couple of times and reading about your symptoms of a worn bearing, I got to thinking. Has anyone put a stethoscope to their table? Much should be heard from one. So I went down in my basement and dug out a stethoscope I have for listening to motors, I use for cars and motorcycles. This thing is pretty damn sharp. Picks up the slightest sounds. This type of stethoscope has a thin, solid, metal rod for holing against a subject, as opposed to a big round pad that a doctor would hold up to your chest.

When listening to my Denon, placing the rod around the platter while it`s running, I can only hear the slightest sound of the motor running. A pretty consistent, smooth sound. No thumping, jarring, or anything that might suggest a worn bearing component. It was good to hear.

But, I am still interested in getting a look in there and give everything a good cleaning and inspection. Sure wish I knew someone that has accessed this model. I don`t want to start randomly pulling screws from below the platter, without knowing what I`m loosening.

I am assuming your bearing was accessed from the top of the table?

Happy New Year. ..... Serge
Serge,
No the motor is removed from underneath the plinth. There are four screws that hold a shield around the motor and an additional four screws that hold the motor to the assembly where the platter spins. The motor plug is a plastic molex type plug with three pins on the DP-62L.

The toughest thing is removing all of the screws that hold the thick bottom cover over the bottm of the plinth. You first remove the platter, then I used rolled up pieces of bubble pack to place between the dustcover and the tonearm and top of the plinth. I placed a clean soft towel on a flat working surface and inverted the turntable on its dust cover.

After the bottom cover is removed I had to cut one tye wrap and unfold one soft metal cable tie down to free the wires coming from the motor. Once that was free I unplugged the motor and removed the screws that hold the shield around the motor. One of the screws has a black wire that goes to a ground point on the main PCB. Then I removed the screws that hold the motor under the platter assembly.

You then lift the motor out of the plinth.

Ed

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Re: Bearing Maintenance

Post by BlueRob » 05 Jun 2019 14:47

I will resurrect this thread...hopefully some one can help. Same issue My Denon DP-40F is in need of a thrust plate apparently. Can someone point a source to acquire one or maybe some DYI options.

All started when the platter started rubbing the top part of the magnetic speed sensor. The platter seem to ride a tad lower than it should. After disassembling the spindle motor I only found a dimple at the bottom.

Thanks!

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Re: Bearing Maintenance

Post by xczar » 25 Jun 2019 15:14

BlueRob wrote:
05 Jun 2019 14:47
I will resurrect this thread...hopefully some one can help. Same issue My Denon DP-40F is in need of a thrust plate apparently. Can someone point a source to acquire one or maybe some DYI options.

All started when the platter started rubbing the top part of the magnetic speed sensor. The platter seem to ride a tad lower than it should. After disassembling the spindle motor I only found a dimple at the bottom.

Thanks!
Howdy, though I only occasionally catch up on topics here I noticed your post. It is interesting that your platter did this. I`m guessing you believe the platter is sinking due to the wear of the main bearing components? Sounds like you got in there to inspect?

I would be very interested in knowing what was involved, maybe pictures if available? If all you need is a thrust plate and no new replacements are available, I would believe making one would be a possibility. But I`d love to see the part itself.

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