The greatest tweak for a turntable........

[marcmorin]

chiming in here late........first, we're not measuring friction, in the pure sense of the word, we're measuring rolling resistance of the ball(s) in the race to the (pre)load applied.
second, how and where the rolling resistance is measured is not an industry standard. in the basic 9" arm, the mechanical advantage of the headshell end is approx 7-1 ratio.
If a manufacturer claims 7mg of "friction" (rolling resistance) at the bearing, 1mg of mass added to the headshell should start movement. Betting the claim of 7mg at bearing is either the bearing measured free, or they've added 7mg at headshell end and claiming the 49mg of rolling resistance to be in fact only 7mg.

 

[bimasta]

It was some Jelcos I'd been checking out at 30mg.

So Jelco arms should be prime candidates for Wyaner's tweak: 30mg is very high, compared to other arms, and should be adjusted lower. On the other hand: everyone likes Jelco arms, fine instruments for the price.

So maybe it doesn't matter. Jelco chose 30mg, it's not an accident. They use the same type bearings and could easily adjust them lower, but they prefer 30mg. This flies in the face of audio orthodoxy, which has many 'absolute truths' that must be heeded — one is that arms should have the lowest possible resistance to movement. But orthodoxy also has blatant contradictions coexisting with its absolute truths. Maybe arms should have user-adjustable bearings, "adjust to taste", like salt in a recipe. I read a recent review of a new super-expensive tonearm that offers adjustable bearings (I forget which one). Wayner adjusted his mainly by listening*, not by measuring micrograms or millionths-of-an inch (SME claims it adjusts its bearings to the correct millionth-of-an-inch).

Theoretically there's one 'correct' VTA, so why have VTA 'on-the-fly'? Because we hear the difference. I adjust VTA so it sounds best and consider that to be the 'correct' setting. HTA (horizontal tracking angle, usually called overhang) is so important we may spend 2 hours with protractors and magnifiers trying to get it right, and only one setting is 'right' — so much easier to adjust it on-the-fly. VTF also matters, and wish I could adjust my counterweight on-the-fly.

If the goal is "The closest approach to the original sound", as Quad's founder Peter Walker put it, anything that gets me there is valid, even if it's not 'correct'.

* I don't mean to oversimplify Wayner's method; he's a pro and I assume he had many criteria in mind while listening.

 

[likebike23]

Used equipment, fixing things, tweaking to optimize, etc are all things that not everyone is willing or able to take on. Like Wayner said, there is an element of bravery involved, a confidence that one is capable of handling a job.

I fixed office machines for 8 or so years and the skill and confidence to get the job done were something that I had to develop over time. If someone picks up a $5 turntable at a tag sale that is all f'ed up and headed for the trash then I say what is there to lose? We learn how to do things by doing them and maybe making a mistake or two. That's part of the deal, if you don't have the stomach for it then that's ok. No need to derail a thread that might appeal to those who do have the stomach for it.

 

[marcmorin]

So Jelco arms should be prime candidates for Wyaner's tweak: 30mg is very high, compared to other arms, and should be adjusted lower. On the other hand: everyone likes Jelco arms, fine instruments for the price.

as noted in my reply, it depends on where the 30mg is being defined. if it takes 30mg added at the headshell to get the arm to move when zero floated, then the rolling resistance at bearing would be a whopping 210mg of resistance at the bearing itself. if 4mg added to headshell, that's 28mg at bearing

 

[embrown057]

I strongly suggest unless you have some measuring gauges your results may not be as spectacular. I've seen a few over the years of being DJ bag boxes have damaged beam bearings. Usually the bearing to pivot has play, not sure why it would be tight. I don't doubt the OP has a result, I'm just a numbers guy. If I had one mod to suggest it would be purchaser one of Ken's fluid dampeners for the beam.

 

[WaynerN]

I strongly suggest unless you have some measuring gauges your results may not be as spectacular. I've seen a few over the years of being DJ bag boxes have damaged beam bearings. Usually the bearing to pivot has play, not sure why it would be tight. I don't doubt the OP has a result, I'm just a numbers guy. If I had one mod to suggest it would be purchaser one of Ken's fluid dampeners for the beam.

Remember that I bought the SL1200MK2 new in the box, the SL1210 as an open box (told it was returned after 6 days), so I doubt the 1210 has seen any kind of meaningful DJ use, or I would not have bought it.

 

[tnsilver]

.first, we're not measuring friction, in the pure sense of the word, we're measuring rolling resistance of the ball(s) in the race to the (pre)load applied. second, how and where the rolling resistance is measured is not an industry standard.

very good info marc. Likely Technics is quoting the starting torque figures in standard torque units (not SI in Nm but rather in milligram-force per millimeter) as provided by the bearing mfgr. Some concurrent Japanese ball bearing mfgr's like IJK, for example, adhere in this regard to the AFBMA standard that is valid since 1969 (IJK product catalog p-37). It's reasonable to assume the Technics figures are 7mg force at 1mm distance, which is pretty much what you refer to as a free bearing measurement (static state).

 

[DavidTT]

Anyone who adjusted bicycle wheel hub bearings in the cup/cone/race days knows how elementary it can be to make such adjustments. No cyclist worth his shizzle avoided wheel hub adjustments, nor crank hub adjustments, nor steering tube adjustments, and these are on machines that we take downhill at 50+ mph. No reasonable audio hobbyist should be afraid to adjust tonearm bearings. It ain't rocket science people. Screwdriver adjustments and a tiny bit of feel are all we're talking about here. It's pretty difficult to make such adjustment worse then it was at the start, while being pretty easy to make the bearing operation better than it was. It's NOT a high-risk proposition.

 

[marcmorin]

very good info marc. Likely Technics is quoting the starting torque figures in standard torque units (not SI in Nm but rather in milligram-force per millimeter) as provided by the bearing mfgr. Some concurrent Japanese ball bearing mfgr's like IJK, for example, adhere in this regard to the AFBMA standard that is valid since 1969 (IJK product catalog p-37). It's reasonable to assume the Technics figures are 7mg force at 1mm distance, which is pretty much what you refer to as a free bearing measurement (static state).

ummmmmmmm, yep......... One tonearm company may be listing the bearing specs only, while another company lists the amount of mass needed for onset of movement measured at some random spot along the finished piece.

 

[bimasta]

It's reasonable to assume the Technics figures are 7mg force at 1mm distance, which is pretty much what you refer to as a free bearing measurement (static state).

Is such a number of real use? Sure, using a better bearing to start with is common sense — but after adding the mass of the armtube, h'shell, c'wt, and then loading (tightening) the bearing, the final number bears little resemblance to static-state rating. And as Marc points out, manufacturers use very different methods to arrive at a final figure.

AFBMA is new to me; I usually see an ABEC rating — is there a difference in use? Or is it like switching from ounces to grams: the weight is the same.

No reasonable audio hobbyist should be afraid to adjust tonearm bearings ... Screwdriver adjustments and a tiny bit of feel are all we're talking about here ... It's NOT a high-risk proposition.

That's my view David. If it's working well, leave it alone. But if obviously too tight or too loose, I readjust it. I bought a very nice arm used, not long ago. The bearings were very loose, no measurements needed to determine that: it wobbled visibly in the yoke (if that's the right word), and I could wiggle the armtube about 2–3° to either side. It took 10 minutes to readjust them. The method wouldn't meet "lab standard" — I tightened both equally until a bit too tight, meaning the armtube couldn't move up and down freely, then backed off until it did. There was no evident free-play, so I locked it at that setting.

A perfect method? No. But it was a considerable improvement, easily heard in the musical reproduction — much as described in the OP.

 

[restorer-john]

I've got 2x SL-1200mk2s here, one NOS, the other has never been DJ'd and is my current TT in my system. And an SL-1600mk2 (same arm). All have beautiful arms, but I've never needed to touch the bearing screws and collars- so they should be close one would hope.

Also, I have a set of calibrated weights down to 10 mg that I just lent to my Dad. (to check his TT scales were accurate)

Just for fun, we can see what weights at the headshell on a neutral balanced arm are needed for downward deflection. If the 7mg is accurate, the smallest weight (10mg) should easily deflect the arm. Where did Technics rate the arm friction from- the headshell or the pivot/bearing itself?

I can do that in the day or two if anyone is interested.

 

[tnsilver]

Is such a number of real use?

lo and behold it's in the SL-12XX service manual, so yes, it's in use. I suppose we've seen worst, like rumble measurements that mean nothing without the details or 'music power' ratings for amps...

AFBMA is new to me; I usually see an ABEC rating

I'm no expert on bearings but I think ABEC covers tolerances while the older AFBMA (Anti-Friction Bearing blah) covers, as the name suggests, other parameters and torque.

A perfect method? No. But it was a considerable improvement, easily heard in the musical reproduction — much as described in the OP.

It's not "much as described by the OP" it's actually only as described by the OP. It's subjective at best. We have no idea what was before, what was after and what was changed and neither does he. That's because there's ZERO methodology in this tweak. It is not only described by subjective terms it also advocates the use of a subjective methods (i.e. 'some feel') by the common masses (not my words) in the process. It isn't about applying "bravery" it's about turning a screw. A screw that wasn't meant to be turned by us. It was performed without any quantifiable measure of control and it was done obliviously to other implications, such as the centering of the armtube in relations to the lateral pivot.

This "tweak" is old and we've seen it numerous times before. It usually pops up in context of many common cheap turntables where ridiculous tolerances, cheap machining and tapping and insufficient QC, gets the bearings loose in their threads inside the gimbals before the turntable even reaches the customer. This tweak may only apply there b/c nothing can get worst than it is already.

Home use Technics SL-12XX vertical bearings don't get loose in their threads at the gimbals by contact with thin air on their own! If they were getting loose you wouldn't need that spanner tool for the lock screw. You could have just turned it with your fingers. They get loose in doors because owners futz around with them needlessly while offsetting the factory calibration. The way I see it, that's what this tweak is all about. Do it on your own and most chances are - you will make it worst.

 

[WaynerN]

Do it, John......

 

[Jeff K]

IMO, if the slightest rotation of the counterweight changes the zero balance height, and there is no perceptible play when giving the arm a gentle twist and tug, Leave it alone.

 

[JP]

Just for fun, we can see what weights at the headshell on a neutral balanced arm are needed for downward deflection. If the 7mg is accurate, the smallest weight (10mg) should easily deflect the arm.

10mg on the headshell it’ll drop like a rock.

 

[restorer-john]

10mg on the headshell it’ll drop like a rock.

It should.

10mg on the counterweight perhaps.

 

[JP]

I just ordered some 1mg weights. Not calibrated but should be close enough. A ~1/2cm square of 20# paper on the headshell easily deflects the arm on my EPA-100.

 

[marcmorin]

I just ordered some 1mg weights. Not calibrated but should be close enough. A ~1/2cm square of 20# paper on the headshell easily deflects the arm on my EPA-100.

sure it will. Archimedes said "give me a long enough lever and I can move the world" Which is why i don't put much stock into "bearing friction" numbers.

 

[JamVal]

This is a good read. Made me curious as to what minimum weight it would take to deflect my balanced tonearm (Pioneer PL-530)
I don't have any small weights or a scale that can measure an appropriate weight, so I improvised, please check my logic if inclined to do so.

I googled the thickness and density of copy paper:
.1mm thick, (.01cm)
1.2g/cu cm density.
So a 1cm sq piece of copy paper would weigh 12mg.

Post #12 mentioned 70mg should make the tonearm deflect.
So I backed into the size piece of copy paper, 2.4cm sq should weigh about 70mg (please check my logic if inclined)

But how far from the pivot do you place the weight? It would make a difference. As a starting point I placed my 'paper weight' on the headshell.

My balanced tonearm does deflect down when the (70mg) 2.4cm sq of copy paper is placed on the headshell.
So I cut the paper in half - 35mg which also caused it to deflect.
Cut in half again 17.5mg - no deflection.
Going back and forth with different sized pieces of paper gives a minimum of about 25mg is the lightest that caused the tonearm to deflect.

Is that good or bad?

Just when I finally got my null points right now this to fret over.

 

[jrtrent]

Anyone who adjusted bicycle wheel hub bearings in the cup/cone/race days knows how elementary it can be to make such adjustments. No cyclist worth his shizzle avoided wheel hub adjustments, nor crank hub adjustments, nor steering tube adjustments, and these are on machines that we take downhill at 50+ mph. No reasonable audio hobbyist should be afraid to adjust tonearm bearings. It ain't rocket science people. Screwdriver adjustments and a tiny bit of feel are all we're talking about here. It's pretty difficult to make such adjustment worse then it was at the start, while being pretty easy to make the bearing operation better than it was. It's NOT a high-risk proposition.

I'm not sure what a shizzle is, but I'm not worth it. I've loved cycling, but left all mechanical work to the local shop. Same with audio gear, car repair, appliance repair, plumbing, and so on--I'm happy to leave such matters to people who make that their profession.