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DIY SL-1200 bearing mod

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DIY SL-1200 bearing mod

Postby Trackside » 08 May 2012 18:13

I have been reading about the various aftermarket bearings and despite my own measurements of noisefloor and rumble being exceptionally good I decided to buy a new stock bearing and see what I could do myself.It's quite a complex design with lots of materials and interfaces - I suspect this is for reasons of resonance and noise control rather than economy though. The bearing is secured to the chassis by 3 bolts and my first mod was to put a blob of blutack in the well to add some support like the KYB wax mod. Next I dismantled the bearing to examine it more carefully. The shaft is a very close tolerance fit to the sleeve - better than I've see on suspended subchassis decks I've owned. The shaft finish is good under the naked eye but with a magnifying glass it's not 'mirror'. The thrust pad is quite compliant and AFAIK a self healing plastic - clearly built with durability and decoupling in mind. The worst part is however the end of the shaft which is very rough and pitted and not at all what I was expecting. I put the spindle in my hand drill and polished it up with some metal polish wadding. Doing the same to the end just smoothed over the pits so I got some very fine abrasive paper and dressed this up with the drill before finishing off with the wadding (the abrasive paper is much finer than the finest grade wet and dry you can buy BTW). Result was a surface more like a good quality ball bearing which can't be a bad thing. I could have just left it there but I wanted to experiment with different thrust pad materials so I made a new bottom plate from a repair washer with an alloy plate under it so there is a recess for a thrust pad and a metal ring on top to create an oil bath. This was glued together with epoxy metal glue. I had some 1mm thick PTFE sheet and I made a thrust pad to fit the recess and after cleaning everything up I put it back together with some thin fully synthetic motor oil. The spin-down time with the stock bearing (cutting the power) was 18seconds from 33rpm to stationary - with this mod it's 22 seconds so that would indicate friction is down at least. Frequency spectrum of HFN residual noise track shows no dramatic change but I'll test it again when it's been run in a bit more. PTFE is good for minimum friction but it's quite soft and I want to try some harder material which seems to be the thinking with the aftermarket bearings.
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Re: DIY SL-1200 bearing mod

Postby russtafarian » 08 May 2012 20:32

Interesting. Keep us posted.
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Re: DIY SL-1200 bearing mod

Postby dogpile » 15 May 2012 21:13

Trackside. Good work on the DIY bearing!

I replaced my stock bearing with the Applied Fidelity bearing and couldn't be happier :D
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Re: DIY SL-1200 bearing mod

Postby Trackside » 12 Jun 2012 12:36

Update - replaced the PTFE thrust pad with one I made from Lignum Vitae as it's a harder material and well regarded for bearings. The PTFE pad had formed a 2mm wide indent. Replaced the Synthetic gear oil I was using with some Redline 0w10 race oil. This is much less viscous than normal synthetic motor oil, has fewer additives, and is claimed to have a higher film strength and extreme slipperiness!. With the bearing assembled the shaft certainly spins more freely than with either the Technics oil or motor / gear oils. May be too thin for some TT bearings ( certainly for my Systemdeck IIX900) but for the tight clearance techy bearing it could be the ideal oil?. £16 for 1l so not too expensive either.
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Re: DIY SL-1200 bearing mod

Postby missan » 12 Jun 2012 13:35

Another thing that can be done is to increase the oil level so it covers the whole lower part of the bearing assembly. One just has to remember it when moving the TT.
Works good for me with gear oil.
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Re: DIY SL-1200 bearing mod

Postby Trackside » 17 Jun 2012 12:02

My next mod may be to drill a hole in the chassis directly in line with the spindle axis and then thread the hole so I can wind a pointed screw to contact the trust pad plate and couple it more rigidly. I'm not 100% convinced it will work as the original design may be to partialy decouple the bearing from the chassis at certain frequencies (as seen by the various materials that make up the bearing housing) so at least with this mod I can engage and disengage the contact point and measure (and hear ?) any changes.
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Re: DIY SL-1200 bearing mod

Postby Trackside » 19 Jun 2012 09:23

The results are.....
0W10 Redline Race oil is too thin or slippery or both as due to the open ended design of the Technics bearing it seems to drain away. Technics oil may be anti fling to keep it there. Lignum Vitae creates bullseye score marks on the thrust tip but the indentation / wear in the wood is small. I think it's too hard for the Technics shaft material. Delrin works OK, PTFE is a bit too soft. Measuring the noise floor by recording the HFN test records silent groove and running a frequency analysis at the highest sample rate doesn't show any significant differences. Either the changes are blow this noisefloor or there are no changes - either way it's difficult to argue how useful in the real world a better bearing is for lowering noisefloor at least as the real limiter is the vinyl itself. I've ordered some proper Technics oil and will now put in my brand new stock bearing ( with polished tip) and see how it sounds as noisefloor is not the only area of performance effected and my ears are telling me that the harder thrust pad may be creating a cleaner and more detailed sound. Also the screw I've fitted through the chassis to press against the underside of the bearing may well be helping here as well.
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Re: DIY SL-1200 bearing mod

Postby missan » 19 Jun 2012 09:43

Keep up the good work Trackside.

To connect the bottom of the bearing to the plinth is to me a good thing. I have tested this in different ways. But to me doing so it needs to be damped. It would need an interface between the screw and the bearing, that will damp the connection. Just thoughts.
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Re: DIY SL-1200 bearing mod

Postby Trackside » 19 Jun 2012 10:02

My thinking on the issue of the extra support is that the platter has some compliance in the stock setup as the fixing points are above the trust point. This is probably a good idea for longevity as any downwards pressure on the platter from rough handling ( DJ use) will just cause the whole alloy bearing housing to give a little and not bend the spindle which is quite thin. If you press on the edges of the platter you can feel the movement which I don't think is clearance in the bearing. Once you couple the bottom of the bearing making the whole housing rigid with the chassis there could be danger of stressing the spindle with any such force. Obviously in a home situation this is of little concern and a rigid couping may have sonic benefits? Coupling vs damping? - not sure on that one. I'd think coupling would be better to drain any resonances from the platter but damping may do the same?
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Re: DIY SL-1200 bearing mod

Postby missan » 19 Jun 2012 10:12

As I see it neither the plinth or the bearing are especially rigid. So You can look it as the plinth, (with what is connected to it) are coupling it´s vibrations to the bearing, or as the bearing is coupling it´s vibrations to the plinth. Neither is really good as I see it.
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Re: DIY SL-1200 bearing mod

Postby Trackside » 19 Jun 2012 10:39

Resonance control would seem to have been the goals of the designers and at this they were very good IMO at making the right balance of rigidity and damping within the parameters of what is practical in size and weight.
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Re: DIY SL-1200 bearing mod

Postby missan » 19 Jun 2012 12:31

Apologizing for interfering in Your thread. My experience is that it´s very beneficial to address the plinth, maybe the most important, it´s just too week and too little damped IME.

But that is me and You should not take my word for it.
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Re: DIY SL-1200 bearing mod

Postby cafe latte » 19 Jun 2012 13:25

I posted this on the oil thread too, but it has long been a thought to add a small bath to the base of the Technics bearing, maybe a hose clamp with silicone to give a puddle of oil for the shaft to spin in similar to after market bearings, what do you think?
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Re: DIY SL-1200 bearing mod

Postby missan » 19 Jun 2012 16:50

cafe latte wrote:I posted this on the oil thread too, but it has long been a thought to add a small bath to the base of the Technics bearing, maybe a hose clamp with silicone to give a puddle of oil for the shaft to spin in similar to after market bearings, what do you think?
Regards
CL


You can test it just by filling up the space under the bearing, it´s easy to remove if You want to.
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Re: DIY SL-1200 bearing mod

Postby Trackside » 19 Jun 2012 20:11

missan wrote:Apologizing for interfering in Your thread. My experience is that it´s very beneficial to address the plinth, maybe the most important, it´s just too week and too little damped IME.

But that is me and You should not take my word for it.
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No need to apologise :D - improving the plinth is beneficial on all TT's but it's my opinion that the SL-1200 plinth is very good in both rigidity and damping compared to decks of a similar cost. Now when it goes up against the big boys which it is starting to do when it's modded then yes a better plinth is going to help ( as it would with any TT). Can you suggest any mods to the plinth or does it need replacing altogether?
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