Another Jelco 750 set-up question...

[nickbaba]

Decided to post this question as a new topic...
I have just noticed, while fine-tuning the VTA on a newly fitted & brand new Jelco 750, that if I sit my headshell spirit level on top of the arm bearing, (as suggested by Marco in the 750/bass distortion thread), that the bubble is not centred. Its not way off but its noticeably off-centre. (The spirit level is actually sitting on the oil chamber, with screw top removed.)
I would say, if you were looking down directly over the bearing, that the arm is slightly out towards the 11 o'clock position, if you see what I mean.
Firstly, is this even a problem as long as my headshell/cart are measuring flat? e.g. the bubble is centred when at the end of the headshell over the cart.
Can anyone please tell me, if I do need to adjust the vertical angle, is there a way to do that while the arm is mounted?
Cheers, Nick.

[worrasf]

This can happen if the arm pillar is clamped too tightly after adjusting the VTA.
Do you have the standard Jelco arm mounting collar? If so this is also a possible cause which is eliminated by fitting one of Shuggies custom collars.

I have the same arm as you (with a Shuggie collar) and it is truly vertical when just "nipped" up but if over tightened it will throw the azimuth off

Steve

[Ammonite Audio]

Nick has one of my collars.

I don't think that the top of the Jelco's bearing is truly level (mine never was), so it's not a good place to put your spirit level. The best way to ensure that everything is set up true is to first level the whole deck, using an accurate spirit level on the platter (or get one of SRM's levels that fit over the spindle), then check that the armboard is also truly level, adjusting as required with washers/spacers etc (don't assume that because you screwed your armboard down properly to the Techy's chassis that it's true). Once everything is level, you can be pretty sure that the arm pillar is properly vertical with (as Steve says) just a light nip of the grub screw. Only then can you be sure that a small spirit level on the headshell is reading what you think it is.

Be aware that the entire SA-750D armtube can rotate in its yoke if you're a bit heavy handed, so be gentle and make sure that any azimuth adjustments are only made at the headshell.

[nickbaba]

Thanks... I understand. So its a question of making sure that the armboard and TT are level in the first place, then the arm should be level automatically.
Btw, thanks again for the collar, Hugo!

[The Grand Wazoo]

I've moved this thread out of the Technics section and into the general Analogue Art area because it is relevant to owners of all type and makes of TT.

[kor952]

I encountered the same problem with the SA-750LB (with Shuggies collar) on a Scheu Premier. In fact nothing is straight/level, using a spiritlevel along the arm (sticked it with very thin double sided tape to the arm) I noticed that the arm itself is not straight either, especially before and after where the arm is bend.
Leveling a SPU already is a pain in the a.. but when the arm is not straight it is hardly possible to level it.

Ronald.