SP-10 mkII, the next project

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Hi Steve. Although my main turntable interest is in getting the best I can from the SP10 mkII, I have applied the same ideas to a building a plinth for the Teac TN-400 turntable. This turntable had a brief production life before the introduction of quartz lock. It is a servo control design with a discrete strobe and touch sensitive controls. I have only seen the one in the flesh, for which I made a resin plinth. The magna-float is a partially magnetic levitation of the platter to reduce the load on the thrust bearing for performance and wear reasons. Apparently there were legal reasons for Teac to discontinue the TN-400.

It is really quite amazing that you mention the very rare Teac TN-400, because that is the table that I need to build a plinth for!

The plinth you built for it is beautiful.

You are correct, Teac used the 'Magna-Float' technology without paying the company that patented it (also called Magna-Float) for the rights. They were legally forced to sell off their stock of these tables and desist making them.

Back in the 70's, a friend who was working at Federated (a hi-fi chain in Los Angeles) called me up when they got a bunch of these in. Another friend and I each bought one for abut $100.

Years ago I sold mine to yet another friend when I decided to go the belt drive direction, who is happily still using his with a Denon arm. Fortunately for me, my other friend that I originally bought these with, decided (against my recommendation) to buy a cheap TT with built in USB to convert his vinyl to MP3 (the horror) and gave me his Teac mounted on a hard wood plinth.

Now, all I have to do is build a resin/cat litter plinth to replace the hard wood.
 
It is really quite amazing that you mention the very rare Teac TN-400, because that is the table that I need to build a plinth for!

The plinth you built for it is beautiful.

You are correct, Teac used the 'Magna-Float' technology without paying the company that patented it (also called Magna-Float) for the rights. They were legally forced to sell off their stock of these tables and desist making them.

Now, all I have to do is build a resin/cat litter plinth to replace the hard wood.
Thanks for the compliment. It did turn out well.
You might want to remove the transformer from under the Teac chassis. It removes a source of electrical hum and mechanical vibration and further, allows the chassis to sit flush on the base of the plinth for improved damping. The transformer is placed in a screened metal case and triple decoupled by the existing internal grommets and rubber feet.

Buy General Purpose Enclosures Enclosure,metal,aluminium,diecast,black,125x125x75mm Hammond 1590KBK online from RS for next day delivery.

A 4-wire umbilical connects the transformer primary and secondary to the turntable through a 4-pin xlr. I made the umbilical long enough for the transformer case to sit on a seperate shelf. The existing mains cable is left in place.
 

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Thanks for the compliment. It did turn out well.
You might want to remove the transformer from under the Teac chassis. It removes a source of electrical hum and mechanical vibration and further, allows the chassis to sit flush on the base of the plinth for improved damping. The transformer is placed in a screened metal case and triple decoupled by the existing internal grommets and rubber feet.

Buy General Purpose Enclosures Enclosure,metal,aluminium,diecast,black,125x125x75mm Hammond 1590KBK online from RS for next day delivery.

A 4-wire umbilical connects the transformer primary and secondary to the turntable through a 4-pin xlr. I made the umbilical long enough for the transformer case to sit on a seperate shelf. The existing mains cable is left in place.

Sounds like a great idea. For the minor amount of work and parts, I'm sure it provides a reasonable improvement.

What did you use as a mold for the plinth? Did you build one, or use some already existing item?

Did you color the resin, or paint it afterwards?

Thanks
 
Sounds like a great idea. For the minor amount of work and parts, I'm sure it provides a reasonable improvement.

What did you use as a mold for the plinth? Did you build one, or use some already existing item?

Did you color the resin, or paint it afterwards?

Thanks
Built a mold (bottom, sides and an insert the same shape as the cut-out) from screwed together form-plywood with the smooth surface, best for removal of the mold. The raw edges of the insert are taped with smooth grey gaffer tape and mold release is used on all surfaces. The resin is poured in upside down. The top of the pour is the bottom of the plinth, about 30 mm thick. The raw plinth is filled and sanded smooth then sprayed. See post #69. I did not colour the resin. It will not come out smooth enough to use without a surface colour which makes tinting the resin a waste. The mold was destroyed when removing the plinth. In the attached diagram you can see the transformer can is proud of the other metal work. Removing it makes the mold simpler. The plinth is about 90 mm deep with the minimum wall thickness about 30 mm.
 

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..................and I have a factory template which is free to any European member! Goes to the first personal message sender who undertakes that they will not sell it but pass it on to another member when they have done with it! Please give your name and full postal address!;)

Limitation is due to postage costs, NOT to prejudice against any members of any non-European nationalities!!:)
 
User510 - I'm doing a full strip-down of my SP-10, spurred on by your own work with the Technics (so thanks for rekindling my enthusiasm :p).

I have the deck in pieces now, also have removed the end cap exposing the ball bearing in the bearing shaft. As you said, fairly easy to unscrew after a few seconds with a heat gun on full.

Is the ball bearing captive, or can it be removed? I'd like to clean it and expose a 'fresh face' to the bottom of the turntable spindle. I don't want to force anything though so thought I'd best ask first. It seems pretty solidly held in place.

Cheers,

- John
 
User510 - I'm doing a full strip-down of my SP-10, spurred on by your own work with the Technics (so thanks for rekindling my enthusiasm :p).

I have the deck in pieces now, also have removed the end cap exposing the ball bearing in the bearing shaft. As you said, fairly easy to unscrew after a few seconds with a heat gun on full.

Is the ball bearing captive, or can it be removed? I'd like to clean it and expose a 'fresh face' to the bottom of the turntable spindle. I don't want to force anything though so thought I'd best ask first. It seems pretty solidly held in place.

Cheers,

- John

DSC_6308.jpg


What I have discovered is that bearing ball size.....

DSC_6323.jpg



DSC_6324.jpg

DSC_6327.jpg


.........and bore size at the thrust end are the same. This indicates the intent. The ball fits with a light press inside the walls of the bore and in this way has no choice but to find exact center of the bore for the thrust pad on the spindle to stand on.

In practice I found that a small piece of wood doweling can be used to lightly tap the bearing ball out the end of the spindle bushing.

Not much force required. Just be ready to catch the ball.

Fwiw I also checked the rest of the bushing interior for size. It is a straight through bushing with no relief or stepped areas. All the same size.
7.143 mm in dia
The spindle shaft measures:
DSC_6281.jpg


7.123. That leaves .020 mm of running clearance between shaft and bushing. Or .010mm per side. Let's convert that to inches for those of us who think that way:
.020mm = .0008 inches (clearance shaft to bushing wall)
7.143mm = .2812 inches
7.123mm = .2804 inches

Prior to taking these measurements I had taken the following photo:
DSC_6302.jpg


Back lit like it is, one can make out the cross-hatch marks produced by the hone operation during manufacture of this part. Just below that it can be seen that the cross-hatch marks have been worn away by the spindle shaft. I had feared that this might be evidence of severe wear. But measurements in these two regions indicate no measurable differences in size. I'd probably need an air gage to get a size difference between the two areas. I am somewhat relieved. Now to decide if I need to replace the bushing with a new piece or not. I'm leaning toward "not". But I will look at these parts closer on a different day and consider again.

-Steve
 
I'm beginning a similar project in baltic birch and wondering if adding in MDF, either as alternating layers or top and bottom layers, has acoustic benefits? Anyone have any experience with this?

I suspect that the amount of spindle bushing and spindle thrust wear on these 30 year old players will tend to confuse the issue when considering " how much plinth" is needed to achieve the quietest possible background noise levels. (rumble)

But I suppose you could take a plan out of the Lenco modifiers playbook and go high mass baltic birch with a couple of mdf layers. And also a piece of 3/16 inch thick aluminum plate just to enhance rigidity.

Check earlier posts to this thread for some interesting comments.

For myself I intend to experiment with the isophthalic resin/kitty litter as a casting project. I really like the idea of "casting" a plinth as opposed to building one up out of several pieces of wood.

-Steve
 
I'm beginning a similar project in baltic birch and wondering if adding in MDF, either as alternating layers or top and bottom layers, has acoustic benefits? Anyone have any experience with this?

Abone,

Go to Audio Qualia's site and look at the damping factors for different layers of different materials. You need to know the damping before you build the plinth.
Home - Audio qualia
There is so much more to this than you would think.
I read every page before I decided what to use.
I'll bet Porterhouse spent a lot of money and time working up to his end plinth design.

Rush
 
Abone,

Go to Audio Qualia's site and look at the damping factors for different layers of different materials. You need to know the damping before you build the plinth.
Home - Audio qualia
There is so much more to this than you would think.
I read every page before I decided what to use.
I'll bet Porterhouse spent a lot of money and time working up to his end plinth design.

Rush

Thanks Rush,

I'll have to read through this a few times before I fully grasp all that it entails. From my first read however it appears getting my hands on a sheet of panzerholz would be a good bet. Not easy to obtain however though there is a supplier in eastern Canada.
As this will be my first attempt I am thinking building the perfect plinth initially may not be necessary. Woodsong Audio in Idaho builds a wonderful product in Panzerholz at what seems a very reasonable price considering the workmanship. After experimenting with my own, I may end up going that way, if only for the aesthetics.

What did you end up doing?

Andy
 
What I have discovered is that bearing ball size and bore size at the thrust end are the same. This indicates the intent. The ball fits with a light press inside the walls of the bore and in this way has no choice but to find exact center of the bore for the thrust pad on the spindle to stand on.

In practice I found that a small piece of wood doweling can be used to lightly tap the bearing ball out the end of the spindle bushing.

Not much force required. Just be ready to catch the ball.

Fwiw I also checked the rest of the bushing interior for size. It is a straight through bushing with no relief or stepped areas. All the same size.
7.143 mm in dia
The spindle shaft measures:

7.123. That leaves .020 mm of running clearance between shaft and bushing. Or .010mm per side. Let's convert that to inches for those of us who think that way:
.020mm = .0008 inches (clearance shaft to bushing wall)
7.143mm = .2812 inches
7.123mm = .2804 inches

Back lit like it is, one can make out the cross-hatch marks produced by the hone operation during manufacture of this part. Just below that it can be seen that the cross-hatch marks have been worn away by the spindle shaft. I had feared that this might be evidence of severe wear. But measurements in these two regions indicate no measurable differences in size. I'd probably need an air gage to get a size difference between the two areas. I am somewhat relieved. Now to decide if I need to replace the bushing with a new piece or not. I'm leaning toward "not". But I will look at these parts closer on a different day and consider again.

-Steve

Thanks so much for that information Steve - really helpful. Great pictures too! Wondering whether I should leave the bearing where it is, or push it out now. Pushing it out might lightly score the sides of the ball bearing?

Did you find a flat spot or evidence of wear on the ball bearing from where the spindle had rested upon it all these years? I imagine the 'plastic' (Teflon?) button at the bottom of the spindle is designed to be softer than the ball bearing though. If there was no flat spot or mark on yours, I guess there'd be no point in removing mine.

John.
 
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