Turntable Bearings

How can we tell the condition of a used TT bearing with a good and reasonable accuracy other than just observing it?
There are different types of bearings that are used in turntables. In the most common type a male shaft rides on a ball inside of a bushing.

Removing the male shaft and looking for uneven wear on the bottom of the shaft, where it contacts the ball, is the place to start. Also remove the ball at the bottom of the well and see if there is any eccentricity or uneven wear. Cleaning it free of oil and rolling it across a glass table can help. It is a bit harder to assess wear in the bushing but once the turntable is reassembled, rock the platter, or sub platter, gently and see if there is any play. Most turntables - though not all - should have very little, or no, play in the bearing.

While you have the darned bearing apart, it might be a good idea to sop up all of the old oil and reoil the bearing in accordance with the manufacturers requirements. You should see no metal debris or filings in the old oil.

Just an FYI, it's much easier to give an accurate answer to these types of questions when the make and model is spelled out.

Good luck and happy listening.
Thanks, maybe I should have been more specific. I'm looking to buy used, I have a 1980 version of a Linn LP12. The lower registers seem a little diffuse now and I'm told thats a symptom of a worn bearing. I can't see it but I can hear it.. So as clarification I'm not asking about obvious wear that's easily observed but instead I am concerned about a used purchase with undetectable wear by the eye. I would try an o-scope but I'm not exactly sure how to set that test up.I also use a stethoscope. I believe that after 40 yrs any bbearing must show wear even if it's unoticiable.
Also people ask for advice and I can't fully establish that a bbearing on an older table is good. Looking at an older Linn doesn't tell you much unless the wear is extensive.
I hhope that helps.
You can easily replace the bearing on an LP12, contact Rick at audioalternative.com, he is a LP12 guru. If anyone knows these tables top to bottom it would be him.
Thanks; still don't see how to check an older bearing though. BTW, Linn doesn't sell older replacement bearings; only the new ones for 1300$
Still might worth a call to Audioalternative as he may have bearings removed when people upgraded. Just a thought, also he can probably tell you what to look for when inspecting yours. Off hand I would say remove the subplatter and clean all the oil from the bearing well and look inside for any roughness and also the end of the shaft. Also as a previous owner of an LP12, if the suspension is not correctly adjusted, the sound quality can be affected greatly. They are a great sounding table but very finicky which is why I sold mine. You haven't mentioned how long you have had the table, so the following may be redundant and no offense is the intent.
A quick test of the suspension is to find the point between the spindle and the tonearm pivot point and quickly tap your finger enough to depress the platter. Then watch the surround of the arm board and see if it bounces in a plane where the gaps around the arm board stay the same. If it shifts in any direction, adjustment is probably needed.
Try posting your question on the Linn LP12 forum on the Linn site. Several LP12 experts frequent that forum and you're more likely to get answers.
$1300 for a Linn bearing? Are you sure? Anyway, I have an NOS one around here someplace. The question is where?

In any event, replacing the bearing may not be your only course of action. If possible, replace only the ball. I cannot remember if it is fitted to the shaft, or not. Regardless, if it is damaged, that could be your problem. If slight bearing is indeed the problem, you might want to try a heavier lubricant. I know some Linnies won't agree, but there is nothing mystic about the factory oil. A heavier oil will compensate for slight wear.
The Linn bearing does not employ the use of a ball bearing. When upgrading the Linn bearing which is part of the inner platter, Linn recommends changing the outer platter as well to ensure complete balanced and matched interface.

Since your table was produced in the 80's, you can purchase an upgraded bearing, inner platter and outer platter kit called the "Cirkus" upgrade.
The new Cirkus upgrade costs 1300 and no one will sell any NOS bearings. The issue is how to tell wear on any used 25 yr old table bearing and spindle. If you can see it; then it's too far gone to even consider as a purchase. So what thhen?
The Linn bearing has a very tight tolerance. When used with the recommended Linn black oil, the spindle should slowly float down within the bearing well, sometimes taking minutes to settle. If it drops too quickly, the tolerance may be off. With respect to wear on the point that comes in contact with the thrust plate, spin the platter ( without the drive belt), the platter should spin freely for a prolong period of time. Also, you can purchase an inexpensive stethoscope and listen for bearing noise, but you need to know what to listen for as you currently have no reference point.

Yes, it is difficult to find a nos bearing and that is due to the fact that the bearing and platter were sold as a set. A lot of people have upgraded to the Cirkus bearing, therefore, there should be a lot of used but excellent condition old bearing/platter combo that can be purchased for an excellent price.
Yes; tried the stethoscope and seems o'kay. Consulted with two known expert Linn tech's and they seem to agree that thirty yr old bearing should be replaced regardless. No 1st gen Cirkus NOS available so the new Cirkus is the only option. Now to restate my question; does anyone recommend the purchase of a thirty year old TT with no way to conclusively determine thhe viability of the platter spindle and bearing? I would like to sell this table to a friend but not w/o being able to assure him of it's value. I know I could try for an NOS bbearing from Russ Andrews but I'm not sure it would fit in with my existing sub-chassis. I see a llot of older tables for sale and wonder if anyone really knows if the bearings are not worn into audible problems; even if you can't see the wear. BTW; thanks to all for the very informative and kind responses.
The new(er) bearings will fit in the older tables. There are literally thousands of 30 year old LP12 in service with their original bearings and existing owners are not complaining. If you like the Linn sound, an older LP 12 with an Ittok arm in for around the $1k range used is hard to beat.

Btw, you can always purchase a cheap digital USB microscope and check for a flat spot on the spindle point.
Yes, if the price if right, and the platter spins freely, I recommend the purchase of a thirty year old turntable with no way to conclusively determine the viability of the platter, spindle and bearing. These things sell every day.

Of course, if one has audiphilia nervosa or OCD, maybe not.
Microscope! That's the ticket. To address OCD;I agree to some extent; I know it appears a little overzealous to question the bbearing condition like this. But let me say this. I stated earlier that the bass sound seemed to be more diffuse and not quite as sharp and detailed as it was initially. How do I know? My only defense is I hhave owned the table for 30 yrs. I like to listen. If I felt I could not seriously tell these things then I would take up golf and buy a BOse system. But I trust my ears and this is my hobby and if you can't do that then whats the point? Please not to sound harsh it's just how I feel.
To answer your question, one must first determine the value of the table in what you believe it's current condition to be. I sounds as if you are somewhat confident that there is/could be an issue with the bearing. At this point, walk away there are many many of these LP12's in various states of condition and upgrade on the market. You can buy a LP12 from a dealer as mentioned for as low as 2000.00 that he would have gone thru. I know Rick would not let a "problem prone" TT out of his shop. He may and will suggest upgrades as that is a dealers path of business to LP12 owners. As far as what will fit the oldest LP12, anything Linn produces will retro fit their LP12's. They never have changed the base units, just keep adding upgrades,e.g. motors, bearings, suspension, arm boards, tonearms, power supply's and the list goes on. As a former owner I decided to move in another direction as the desire to upgrade would have been too expensive. But with out know what dollar figure you are looking at on this particular LP12, it is hard to justify if you have to turn around and spend 1300.00 right away. If you could buy a ready to go and properly tuned table for 2000-2500.00 I know where I start.
All my opinion of course. But from what I am reading, you seem very concerned about this table's bearing and, I have found my fears/concerns are usually warranted. If you are hearing something that doesn't sound right, it probably isn't and LP12's are a expensive when trial and error trouble shooting them.
Again just my opinion and no intent of offensive content.
When was the last time you had your 30 year old LP12 serviced or tuned? That would have a MUCH greater impact on the sound than bearing wear. Perhaps, time for new springs, grommets, and a suspension adjustment.
Thanks; The table was last serviced about three yrs ago but it sits on a shelf and doesn't move and I'm very carefull about it's use. As for the upgrade path; I wanted to install a Cirkus bearing last November but it seems I was a couple weeks too late and the 1st. gen Cirkus was discontinued and the new Cirkus was introduced. At significant price increase. I want to state that I don't question the quality and improvement in sound the new bearing would provide; I have heard one mounted on an older Linn like mine. I'm borrowing a binocular microscope from a friend. I'll keep this forum posted regarding my personal opinions and findings; FWTW.
I would like to establish here that this is fun for me; learning these things. And thanks for all the help from everyone.