How Do You Know Anti-skate Spring Has Enough Tension?

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Sleepwalker65
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How Do You Know Anti-skate Spring Has Enough Tension?

Post by Sleepwalker65 » 12 Jun 2018 03:19

This is bothering me. I’ve seen the instructions on how to calibrate the anti-skate knob on a SL1x00mk2 turntable, but when I set it up, it seems the spring doesn’t have any appreciable amount of tension in it. Consequently, dialing up the anti-skate knob while the arm is floating over the platter has zero effect. The arm just remains in the same position. Does this mean the spring does not have enough tension to counter-act the arm’s tendency to move towards the spindle, or are my arm bearings shot? For what it’s worth, I can't detect any “slop” in the bearings.

As always, thanks for the knowledge!

Gelid
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by Gelid » 12 Jun 2018 03:32

A good standard is to center a blank CD or laserdisc on the platter, set antiskate knob the same value as tracking weight (1.5 grams tracking weight = 1-1/2 antiskate) then lower stylus onto the disc surface with it spinning on 33-1/3 rpms. It should remain in the spot you lowered it, but it will prob move in or out... tweak the antiskate knob until tonarm stays put.

chiz
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by chiz » 12 Jun 2018 11:57

Sleepwalker65 wrote:I’ve seen the instructions on how to calibrate the anti-skate knob on a SL1x00mk2 turntable
These ones?

(from the service manual here: https://www.vinylengine.com/ve_download ... ervice.pdf)
antiskate.JPG
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analogaudio
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by analogaudio » 12 Jun 2018 19:17

To answer your question: it is not necessary to know the spring tension because Technics already figured that out when the unit was designed and manufactured.

It is necessary to verify that there is no damage to the spring or the mechanism. Then assemble the "canceller" spring correctly and the job is done.

Sleepwalker65
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by Sleepwalker65 » 12 Jun 2018 20:12

analogaudio wrote:To answer your question: it is not necessary to know the spring tension because Technics already figured that out when the unit was designed and manufactured.

It is necessary to verify that there is no damage to the spring or the mechanism. Then assemble the "canceller" spring correctly and the job is done.


I have doubt that the spring has sufficient tension. The prior owner of the turntable in question was a “DJ”/rapper who beat the crap out of it. It’s a SL-1700mk2, which is extremely rare to find, regardless of condition. Now, I’m left to put this turntable back into operating condition, which hasn’t been easy. As I said, I am doubtful that the spring was unharmed... I’m sure that Technics did a fine job of designing the spring, but they certainly didn’t anticipate the abuse this poor thing endured. One of the best things about the SL-1700mk2 is that it has all of the best attributes and parts of the much-loved SL-1200mk2, but adds a better chassis / plinth suspension to cut out communicated vibrations, and has an auto-return function on the tonearm at the end of play, that creates zero effects on the stylus tracking. So, this particular turntable is very worthy of being rehabilitated.

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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by analogaudio » 13 Jun 2018 18:33

There are many ways these fine units can be damaged by DJ abuse however the AS spring is pretty safe. The manufacture of springs includes a process called tempering, following this the spring tension remains set forever. The spring is buried inside inaccessible. The DJ could turn the AS knob back and forth a thousand times a night and not wear out the spring or damage it.

If the unit was dismantled by someone and the spring damaged that is a different story however simply removing and replacing a spring using care does not cause damage.

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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by Spinner45 » 13 Jun 2018 20:17

For every 1 gram of tracking force, roughly only 0.12 grams of anti-skating force is needed.
Any excessive friction of the horizontal pivots (due to abuse/wear?) will not give a "visual" indication of the control working properly.
So with that said, if the skating dial is set at 3 grams, the "pull" is around 0.36 grams, and if no movement of the arm is noticed, the bearings are crapped up.

Sleepwalker65
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by Sleepwalker65 » 13 Jun 2018 22:25

Thanks Spinner45 for the detailed explanation of actual anti-skate force vs the control setting. This makes me believe that, unless the end of the spring is caught up in the plastic housing (which I’ve noticed a few times during disassembly and reassembly of the mechanism), I’m likely in need of a new set of bearings. I suppose in that case, it’s easier to source a complete set of gimbals with the arm tube and bayonet. Wonder if there is any new “old stock” inventory out there at Panasonic or through other sources (KAB?).

As always, thanks for the knowledge.

Sleepwalker65
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Re: How Do You Know Anti-skate Spring Has Enough Tension?

Post by Sleepwalker65 » 15 Jun 2018 07:34

More progress made tonight on figuring out this headache. I stripped down the tonearm base to just the bare essentials, and set it up for the standard anti-skate test. Not surprised when the arm stayed put no matter how much anti-skate I dialed in... so I checked to see if the top and bottom bearings were binding up. I loosened the top bearing locknut after considerable effort. The bearing screw was seized up (not surprising after nearly 40 years), but it eventually moved. That released the death-grip on the ball-bearings, and the arm is now free at last! I took a very fine insulin needle and put a few droplets of fine machine oil at the fulcrum point of each bearing, then did the anti-skate float test once again, and it faithfully returned the arm back to the arm rest. On top of that, the tonearm moved super-smoothly in all directions now, and there’s no slop in the bearings. This weekend I hope to get the tonearm rewired with recently purchased KAB Superflex silicone litz wire, and get down to spinning some tunes at last.

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