Restoring and Improving A Thorens TD-124 MKII

[user510]

Originally Posted by brianco

A possible property of such metal which causes the mentioned 'damping' effect is that the larger-flake graphite content is responsible. It is reasonably well known that carbon will turn vibration into heat. If this is in fact the reason then some vibration will be dispersed. [I have two purest-carbon platter blanks waiting for use: one will certainly be bonded to the existing platter of my Lenco, whilst the other will be used on a simple string drive DIY TT.]

Thank you for the link to Art Dudley's article; from there I travelled to his review of Mr Schick's tonearm. It was most interesting.

I suppose this information would be in agreement with the idea of using solid graphite to machine a platter mat from. Like the Boston Audio Mat-1.

I do like your idea of using graphite as one layer of a platter assembly. Hmmm, I wonder; aluminum/graphite/aluminum ...as a sandwich?

Or perhaps; grey iron/graphite/aluminum as a sandwich.....

Not necessarily as a TD124 platter but for something larger like a high mass belt drive platter, or an idler drive platter like the Lenco....

-Steve

[brianco]

Steve....

I have experience of such TTs.

Be Yamamura made a few TTs which were almost 100% carbon. These were unique in that they were total air float platters. the platter rim was a machined bronze periphery ring. I have also seen his more normal air float (as per various Japanese TTs.). He did not sandwich the platters with anything, but a plate glass lower surface makes sense if air floating with a normal bearing for horizontal control. Any sandwiched material will, I guess, interfere with the travel of vibration by causing a reflection thus returning the vibration toward its source with predictable results. However I would seriously think that a carbon mat to fit on the top of the under platter on a 124 would be a great success. (put the alloy one away and remove its lifting gear as it vibrates like anything!) The carbon needs to have the finest granular composition that you can afford. And whilst at it get three or four pucks to use as feet for your 124 plinth, with another, infinitesimally higher, than the between the bottom of the main bearing to the top surface of whatever your TT sits on. [Similar effect to the cast iron vibration sink that guy on the other site uses in his SP10 plinths.] If you get a mat made ensure that there is a straight incline toward thye centre giving a ) 0.4mm drop toward the centre, and use a record clamp. The ideal thickness of mat is as thick as possible, but it should ideally be at least 15 mm thick, and I would estimate, ideally about 1" on a 124. All surfaces should be highly polished and then sealed with a thin coat of aerosol hair lacquer or similar.

[user510]

There is a product name for the non-magnetic iron alloy we seek. It is called "Ni-Resist".
This is most likely what Schopper is using in his non-magnetic platter.

Category name; Austenitic Iron

The gray iron is alloyed with a high percentage of nickel along with a small amount (1/2%) of copper. There is more than one alloy available. I keep turning up two alloys of Ni-Resist. Type 1 (201 Ni-Resist) with13.5 - 17.5% nickel and Type 2 (202 Ni-Resist) with 18 - 22% nickel. Among the properties description in these alloys the term "non-magnetizable" will be seen.

This trade name does indicate the presence of graphite flakes in its micro-structure. This is consistent with the advertising propaganda that Schopper is using.

From what I've been able to turn up in web searches, it is common to find this material in the usual forms of stock for machining. Round bar and plate. Typically, round bar sizes listed will only go up to 6 inch diameter but with the notation that larger diameters can be produced on special order. That's likely too expensive for the economy of diy turntable making. But perhaps a wider search can turn up some plate stock of adequate thickness that can be sawed and milled into a round shape that could then be chucked up in a large engine lathe...... or cnc turning center..

Ni-Resist. That's what he's using.

-Steve

[his047]

Are there any of you that have tried to modify the idler wheel bearing to turn it into a ball bearing? any experiences, pitfalls ... no-nos?

[kevinkr]

Originally Posted by his047

Are there any of you that have tried to modify the idler wheel bearing to turn it into a ball bearing? any experiences, pitfalls ... no-nos?

I would expect a ball bearing to be significantly noisier than a sleeve bearing. Note that the motor, and intermediate (stepped) pulley also use sleeve bearings.

[his047]

I know that all the other bearings are sleeve bearings, but I would have thought that the vastly reduced contact area of a set of ABEC 13 bearings (or similar) would reduce the noise.
In the meantime, though I have changed the bottom centre bearing using the kit provided by jec965, and I must say that that has totally bowled me over and obviated the need to reduce the noise from the idler wheel: my TD124 is now as silent as my SOTA belt-drive was. I cannot recommend it highly enough,particularly now that he has changed the Cork washer for Teflon.

[kevinkr]

I have a lot of his parts on my two tables, all seem to work quite well. The only audible noise my 124/II makes is the noise from the eddy current brake which is quite low level. (This is about 9 - 12" from the platter) The 124/I is a bit noisier, but not noisy per se.

Both tables have rumble levels that appear to be lower than most cutters used to make records. IMLE recent pressings generally have the lowest levels of rumble I've heard.

[his047]

Have you tried damping it? I am toying with the idea of using plasticene (modelling clay) to do this.

[volken]

[QUOTE=kevinkr;2992173]I have a lot of his parts on my two tables, all seem to work quite well. The only audible noise my 124/II makes is the noise from the eddy current brake which is quite low level. (This is about 9 - 12" from the platter) The 124/I is a bit noisier, but not noisy per se.

Kevin makes the brake noise or do you mean the bearing from the steppulley ?

regards

Volken

[his047]

I did something that most people would shake their head at since it is so counterintuitive, but which actually lowered the noise level to way below cutting/surface noise: I gently applied a wet wet/dry sandpaper (1000 grit) for one minute to the motor pulley, step pulley and the idler wheel. Result: virtually no residual noise. Highly recommended.