Zeta Tonearm - Top bearing Horiziontal Plane adjustmet

[tutancarmen]

Hi ,
I've got a Zeta tonearm . While i've found relatively easy to adjust the vertical bearing play, not the same can be said for the top bearing that move the tonearm in the horizontal plane. I've made it by ear with a record of choral music orchestra . The result I've obtained is nice but I've noticed , that small adjustmet of the top bearing screw affect really much the sound . I've dismentaled the arm but indeed I don't understand how to obtain the properly adjustment as the manufactuer intended when designed it .

[karma67]

hi,
i have rebuilt 3 in the past,i used a mechanics stethoscope and gently using your thumb and finger rock the arm tube from side to side and listen for any play in the bearings,you need a bit of play obviously, aim to get it so you cant feel any but you can just hear a faint rattle as you rock the tube from side to side. its something you get a feel for after a few trys.

this is all a balancing act though as tightening up the bearing cover also can tip it over the edge and become to tight as does the grub screws for locking the bearing cap.
in the video i am lightly blowing on the arm block.
https://live.staticflickr.com/1782/42236736304_02bce757b7_o.jpg (https://flic.kr/p/27mjjcs)IMG_2372 (https://flic.kr/p/27mjjcs) by , on Flickr

[tutancarmen]

Thanks, I'll try as you suggest to me. Are you telling me that until you cannot hear that faint rattle the bearing are not free enough ?

[karma67]

you have to have some play,try concentrating on getting the tonearm to glide smoothly across the platter.dont worry about putting the bearing cover on at this point,if you over tighten you will see how the tonearm responds,it wont be a smooth gentle swing.very small adjustments are needed,slightly too loose is better than slightly too tight.
you should be able to lightly blow on the arm and it should travel across the platter with ease and with no sticking.

[tutancarmen]

Indeed in that way the tonearm works great . What does a Mechanic stethoscope use for ? Is it in the picture you sent me?

[karma67]

Click on the picture, it’s a video.
The stethoscope amplifies the sound of the bearings for checking the tolerance. In the same way a doctor uses one