Turntable Bearings

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?